I've finally decided to make a thread about this. On the textures page it clearly says that .PNG file-types are allowed gile-types to upload a texture as, and I as a texture maker find PNG the most convenient filetype to send to people (it is allowed on imageshack and i can send them the thumbnail of their texture), but my customers always complain that the flat PNG image that i send to them never appears on their tori after long periods of waiting. I'm tryin to figure out why they never appear, its not something im doing wrong, because it seems like PNG is not allowed when it really is.

hhmmp make sure it is not interlaced or somthing.

Ask your customers if they uploaded their texture successfully or not. It might be their PC/Connection/Toribash problem.

[And make sure that you "obey" to all the other texture rules]

most common cause: greyscale pixels only.
if that is so add a dot of colour to the bottom corner, wont be visible and should work

Hey, 1 problem could be what the colors are saved as.

Working files save as just RNG, but ones that don't work (which is how I fixed mine) save as RNG Mono.