I successfully uploaded a couple of skins with a blank white alpha file added, bar the reference image file that I accidentally misnamed. It took about 2-3 minutes for the 1024 res skin and 7-8 for the 2048 res one.
Many of the GVs still have some track files incorrectly listed as required, these are the files:
Firefly: a, e, p
Hetzer: e, p
M16: e, p
LVTA4: e, p
M18: e, p
M4A3 75: e, p
Panzer IV H: e, p
Panther: p
T34 1943: a, e, p
Tiger I: e, p
Tiger II: p