How about running the textures through some sort of compression algorithm, turning the compressed data into Data statements, then rebuilding the textures internally at runtime (uncompress data, CreateTexture/WritePixel)?
There are a couple of compression algorithms in the Code Archives that could probably be modified to write to Data statements and read into bank and/or texture.
There are a couple of compression algorithms in the Code Archives that could probably be modified to write to Data statements and read into bank and/or texture.