Meanwhile it is possible to inject textures into painttool on 360 with KG971's tool. Luckily his tool works for PS3 too.
Its Tough, But doable.
1. Get the Tools
KG971's tool
wxHexeditor
Le Fluffie
360 Save with Painttool file
2. Create your textures with paint.net/photoshop or whatever and save the file as DDS file (8.8.8.8 ARGB | 32 bit unsigned, only 256 x 256).
3. Start KG971's tool, load the 360 save (SaveData.dat) go to the Paintool file section and open the 00PaintTool.pt f