There are some things, which need to be done or replaced, and which would be greatly appreciated:
Icons, which must be replaced anyway:
AAX Prime, Allied Legendary Mech/unit.
Allied Heavy Trooper.
Allied Command Headquarters.
Allied Special Forces (Delta Force).
Allied Oil Derrick.
Yuri Mind Destroyer, LU.
Allied Nemesis Bomber.
Soviet Battle Fortress, Sabertooth.
Soviet Tank Bunker.
Yuri Lieutenant (only making it more Yuri-like, just look at its Soviet background ;-)).
Icons, which can be replaced or improved (but it isn't necessary):
Soviet Oil Derrick.
Yuri Battle Fortress, Dicero.
Submitted icons must be without any text on them (and w/o a veteran symbol).
You can also help by pointing out public cameos for new units if you find them better than the current bad ones.
Some sounds/voices for various units.
The list of needed voices isn't specified yet, but you can already submit or suggest new sounds/voices for new units implemented to the game (e.g. voices for Gehenna Tank).
Kinds of voices needed:
Voice after selecting the unit
Crush sound (for tanks/vehicles too, you can submit more and different than the single current one)
Sounds for entering and leaving the transport (if the unit has the ability to transport units)
New aircraft (models/voxels), and buildings.
Chiefly basic anti-infantry and advanced aircraft, and new civilian buildings.
Any input will be credited. Anything you send will be considered. ;-)
BTW, it must be your work and your work alone, unless you just point out other's work (public assets on one of websites), or you're sending other's work but you did receive the permission from the author to make it available for use in ASM.