My suggestions (most of them, you've seen already):

1. A pixel bank, with pixel checking and saving accounts, and pixel loans! Loans should be 1-5% interest, and savings should be .05% interest per hour, or per day.

2. Voxels placeable as furniture.

3. Cheaper erchius! Erchius is 100 pixels per, and it should be 5 or less pixels, because that's what it is at Infinity Express. If it was cheaper than 5 pixels per fuel, I'd just synthesize my own fuel instead of buying or mining it, definitely.

4. Smaller voxels. Now that I've used this mod for trading, it's kind of annoying for small purchases, like down to the tens or fives in pixels. So, a full range of voxels, maybe?: 1, 5, 10, 50, 100, 200, 500, 1000, 2000, 5000, 10k, 20k, 50k, 100k, 200k, 500k, 1 million size voxels would be a good range.

5. If you keep adding pixel-related things, you might want to rename the mod to Pixels Plus. First, it has a nice ring to it, and second, this mod seems more centered around pixels than voxels.

--I really like the mod, and I hope it's updated soon! This is my core mod for my modded playthroughs, as it is so useful.

1: Might happen, but will likely be awhile due to the complexity.
2: Already working on a addon that will add compatability with Bloxels. Maybe not furniture exactly, but it will be a building material.
3: Worry not, I plan on repricing the stuff. Those are left over prices from when ou couldn't buy the stuff, hence why the ores are also overpriced.
4: I'll probably just add 1p and 10p for now, but I might add the the other two later.
5: True, although the base idea was expanding the Voxels. That, and I think I remember seeing another mod with that name. I could be wrong though.

OK, and one more thing: what do you use Plutonium for? it can no longer be used as ship fuel..

Pssh, I have no idea. I have a mod I use that makes it work as ship fuel again, but short of mods, I don't think it has one.

Please excuse my spelling as I will likely butch grammar in wirting this...and I am only placing ore and liquids
Berlinite - Phosphorus Ore
Cinnabar - Solid Mercury ore
Densinium - End tier ore to make really tough stuff
Effigium - have yet to find or make this so no clue
Irradium - Have yet to find used in late game equipment and upgrades
Lazulite - magnesium/phosphorus ore
Lead - useful in just about everything in frakkin universe exept food
Magnesite - Magnesium ore
Mascagnite - Ammonium Sulfate ore
Moonstone - mid tier crafting material for armor/weapons/upgrades
Neptunium - ship fuel/mid tier crafting material
Penumbrite - mid/late tier crafting material
Plutonium - ship fuel and mid tier crafting material
Protocite - mid tier crafting material used to make latter tier crafting materials
Pyreite - latter tier crafting material used in lots of weapons
Quietus - latter tier crafting material used in equipment and upgrades alot
Sulphur - part of fertilizer and Magnesium Sulfate or acid
Thorium - ship fuel and a mid tier crafting material
Trianglium - mid to late tier crafting material used fairly common in armor and weapons and for making end tier compound crafting materials
Zerchesium - mid tier crafting material used to make armor/upgrades/later tier compound crafting matterials

Aether - have yet to find the stuff but supposed to be useful in crafting very useful
Alien Juice - crafting material mainly used to make other crafting materials
Bio-Ooze - another liquid crafting material
Black tar - extraction material for oil or a good way to annoy your friends
Blood - crafting material or extract for oxygen
Dark Water - Liquid carbon useful and makes a decent trap
Elder Fluid - end tier material for various crafting recipes or fuel for reactors also causes insanity
Grav-Liquid - used in some recipes and weapon making but mostly a great pranking material or a cheap catapult your pick
Helium 3 - crafting material for making mid to late tier crafting materials like nuclear cores
Liquid Irradium - Irradium in fluid form used in conjunction with solid Irradium
Liquid Iron - great trap material and is used in some crafting
Liquid Mercury - product of cinnibar ore deadly and used in making latter tier crafting materials
Liquid Nitrogen - trap material can be turned into nitrogen which is used in making biofuels
Liquid Protocite - used in conjunction with solid Protocite in armor and some weapons recipes some benefit if bathed in
Liquid Metallic Hydrogen - end tier crafting material for power systems
Organic Soup - great bath and used in making some latter tier crafting materials
Pus - used in making other crafting materials and as a deadly bath
Shadow Gas - Deadly liquid with some use in crafting... I think
Sulphuric Acid - deadly and used in crafting other crafting materials

Lunari Shard - its like finding Diamonds and is used in crafting
Prism Shard - used in crafting
And this just about does it for what I know is actually in use in the mod good luck to you and hope I helped.
* As I couldn't post this in the comments as it was too long had to list it here.

Thanks Bobkat! Do you think you could guess at some prices for the various liquids?

Early tier liquids 20-80 mid tier 80-160 end tier 160-300pixels or something along those lines

Sounds good to me. Could you put the liquids into those three categories for me? Remember, I haven't actually played Frackin Universe. XD

Late Tier - Aether, Elder Fluid, Liquid Irradium, Liquid Hydrogen, Liquid Metallic Hydrogen, Shadow Gas
Mid Tier - Liquid Protocite, Liquid Iron, Liquid Mercury, Organic Soup, Sulphuric Acid, Alien Juice, Grav-Fluid, Bio-Ooze
Early Tier - all the rest

Sweet! Thanks! I'll get to work on it!

shrek critters

While admittedly that would be awesome, that goes beyond the scope of this mod. Try suggesting that to someone who makes critter mods!

Suggestion:
Ever wanted to take on the same banking practices of the real world?
No?
Ever wanted to print completely worthless money just like in real life?
No?
Well now, maybe, kinda, (probably not), you can!
Print multiple pixel credits/certificates which don't actually have any value behind it, more like an IOU for later. Crafted (maybe) with paper and dye!
Perhaps also a currency exchanger that is player specific (owner loads in pixel voxels), and IOUs that go in you get the voxel equivalent!
Perhaps also vending machines that you can set prices, and currency (forcing those who want your items to have to get your currency)...
(Have the currency say the printer/owners name or something to tell its origin)
Take full advantage of capitalism in starbound! Right up until an angry mob chases you out of the galaxy for being completely broke!
^Just an idea though, and a lot of work for something less than useful...

I've been thinking about that, but haven't had a chance to try implementing it. I'll look into it though.

Uh..... can you make a version with only the essence voxels? Sorry, everything looks so good, but I'm looking for a faster Essence storage