1)Photoshop or Irfanview
2)HL2 Animated Spray Maker
Download Infarview:
http://www.download.com/3001-2192_4-10755180.html?spi=72971410b8d797c52a1900b1d8ec035d&part=dl-IrfanView
The Animated Spray Maker is attached to this tutorial
1)Make sure your image is 1024x1024 (not 1024x768)
2)Convert your image in photoshop or irfanview to a 32bit targa file and rename it spray001.tga
3)Open up that spray maker program and go to hl2\materialsrc\animated sub folder. Open up the spray.txt file and edit it so it only has 1 startframe and 1 endframe in quotes. Put the image you just converted into that same folder
4)Now open the convert.bat file that came with the spray program and wait until it tells you to press a key to continue
5)Now open the hl2\materials\animated folder and rename the file spray.vtf to background01.vtf
6)Now open your Valve\Steam\SteamApps\accountname\counter-strike source\cstrike\materials\console
you may have to create the last 2 folders. Put the background01.vtf in the console folder