Ok, for those of you who have tried to use a spray in TF2 and realised it doesn't work, here is a simple method which I'm using to import my own sprays:
Find your image, the sizes must be power of 2 and the final file size must not exceed 512kb.
With VTFedit, Import your own .JPG,.BMP, etc... and convert it to a .VTF file (Valve Texture File)
Now place the .VTF file in: (your dir)\Steam\steamapps\common\team fortress 2\tf\materials\VGUI\logos
To fix the quick view appearing blank copy the same .VTF also in:
(your dir)\Steam\steamapps\common\team fortress 2\tf\materials\VGUI\logos\UI
In game, go to the options and click import the spray and browse for it in the \logos folder (not the UI folder!) and validate. (this will create a VMT file near your VTF)
In summary; your .VTF must reside in the last \logos and also \UI folder where you copied it manually, then don't forget to do the step 5, the spray now appear correctly in the list, I have tested to spray it in game and it works fine.
If you have any problems please let me know in my profile.
1 question why not just do it like this, I don't get why you would use .vtf except for gifs. While making this comment I realized that you probably mean valve severs (which I haven't tested with this yet) but I'll leave this here for people like me.
Instructions unclear, got my d*ck stuck in my Disk Drive. But in all seriousness, great tutorial, but I'm confused at the validation part. I copied the .VTF file to the UI folder, but it's still blank. Do I need to put the UI folder in logos? Or in the VGUI folder? Any help would appreciated! Thanks :D!