Obviously, this is all my personal opinion. Some are much more important than others but just getting all the ideas out there.
My list:
Appearance Tab:
This is the easiest way for a player to customize their appearance. Each piece needs to be able to be toggled on or off, but it is basically a second armor screen, just for how your character looks. Also, in addition to the head piece toggle, I'd love to see an option to toggle hoods up or down on hooded robes. Also, I realize they're attached to the chest piece, but please add an option to toggle shoulder armor off...
Character Creation:
More body types...:
4 is just too few. It really shows when you're playing the game and every other Republic official looks like he's going to send you on a quest for Cheeseburgers. There should be at least 3 more body types in between the existing 4.
More hairstyles:
Sadly, most of the hairstyles in game right now are lazy and many are downright ugly. There are no long hair styles and many are just rehashes of the previous style with some bangs or a ponytail added. Please add some long hair options. You made Lekku work, it can happen. Oh, and "stubble" should be in the beards slider... not complexion.
Better looking faces:
Right now it seems like only the first few options for humans and twi'leks are the acceptable ones. After those few, it is almost impossible to make a good looking character. Please make a quality pass on these and add at least a few more that are even remotely pleasing.
Separate "lazy" tabs:
Eyebrows, makeup and complexion are all one slider. Lekku markings and makeup are all one slider. If more than one thing is being changed, it needs to be a new slider. In addition, make-up and alien markings (Zabrak, Lekku, etc) should have a few color options once the style you like is chosen.
Other:
An in-game boutique/image designer/black market plastic surgery vendor should be added for players to change their appearance at will. (It would be amazing if you could use this vendor to fully customize your companions, too.)
Customization kits for Starships and Vehicles: This can't be too difficult since most have some sort of color scheme already. Think T7 customization kits and you're golden, unless you really want to wow us and go all out with subtle style changes to exterior and interior both.
A bigger dressing room window or at least the ability to zoom.
A weapon dressing room that shows a large view of the weapon you're inspecting.
The ability to "Try on" items that are hotlinked in chat.
User-created, custom guild emblems.
User-created Huttball team logos (or more than two options).
That's all for now! (phew)