is there a way to put wallpaper

in the track space ? if no, whats the name of the png of the track space ?

If you mean the editing area then no, and there is no png for this area.

No, sorry. It's just color choice, no png. Track background (odd) and Track background (even). The empty track area shares it's color with Timeline background and with the field in the transport which shows current position and stuff.

This would be a nice idea though. Some people may find it intrusive, but done right could be good for branding. Digidesign have a nice embossed logo wallpaper. Not sure if it's needed but hey another option ?