I just noticed that Team Fortress 2 is now importing my sprays properly in the Multiplayer Options. Since Beta it had not been working for me. I just tried a 32 bit TGA file with an alpha transparency and it worked fine. This will save me a couple steps when creating the sprays and make it easier for you folks to install em.

Working on a second set of retro war poster sprays since they seem to fit the TF2 theme.