Need Spray Change Help

My Gmod won’t let me change my spray. It gives me the error that it doesn’t fit a set area or that the image is corrupt. What is wrong. Same thing happens for TF2,but no other games.

Make sure the image is 256 x 256.

[editline]10:27PM[/editline]

What does this have to do with Garrysmod.org? You should know where to post this after being here for over 2 years.