As you can see in the bottom-left hand corner of the above image,
I re-textured a part of the gui for the health module about 3 months ago.
A good idea to add onto the gui would be to move the ammo-regeneration timer up and put a module for armor,
and of course a yellow-orange, lua-drawn bar for the armor.
The human and zombie head textures in the top-left can be retextured and other than that, can wait for stuff to get implemented.