If you want to add text or a logo to an existing non-Source map, you will have to rip a new entity into it. This is easiest if you use a sprite.
To do this:
1. Download
BSP Edit and
Sprwiz.
2. Import your image into sprwiz and export the resulting sprite to your sprites folder. If you want text, just throw some text into MS Paint and save it as a 256bit BMP. Your image will have to use a 256-color palette.
3. Load the map you want your logo, and move to where you want your logo to be. Then open the console and type "status". Find your coordinates and copy them.
4. Close your game, run BSP Edit, and load your map. If it's a default map, you will have to use
GFCScape to export the map from the game's gfc in your steam folder so you can load it into BSP Edit. Somewhere in all that code, paste this:
{
"origin" "THIS IS WHERE YOUR COORDINATES GO"
"renderamt" "255"
"scale" "1"
"model" "sprites/NAME OF YOUR SPRITE.spr"
"framerate" "10.0"
"angles" "0 0 0"
"rendercolor" "0 0 0"
"classname" "env_sprite"
}
Save the map to your maps folder and go load it up. Your logo should be sitting there when you go check.
On a side note: If this is really what you're trying to do, please don't do it to a custom map. People who download it from your server will be forced to download your edited version of the map, and mappers
hate it when people do this sort of thing to their maps.