Materials

• Download and compile https://github.com/impiaaa/vtflib-posix
• Use VTFCmd to convert images into .vtf (Valve Texture Format) files

For simple static files, such as backgrounds or logos. Note that the input image must be a power of two size (such as 256x512)

./vtfcmd -file input.png -format "RGB888" -alphaformat "RGBA8888" -nomipmaps -nothumbnail -noreflectivity

See https://developer.valvesoftware.com/wiki/VTFCmd https://developer.valvesoftware.com/wiki/Valve_Texture_Format for more info.

Then place the resulting .vtf file in the mp/game/mod_hl2mp/materials folder together with an .vmt (Valve Material Type) file containing:

"UnlitGeneric"
{
"$basetexture" "path/to/vpk/file/relative/to/the/materials/folder/without/file/ending"
"$vertexcolor" 1
"$vertexalpha" 1
"$ignorez" 1
"$no_fullbright" "1"
"$nolod" "1"
}

See https://developer.valvesoftware.com/wiki/Material for more information