Do you know any doom stand-alone modifications that are playable on n900? I found just wads that need doom2 to work.
And I tried editing with Doom builder 2, I copied and pasted map from another wad too doom2.wad and it crashes on start, so it seems that custom levels doesnt work. (that wad was just some edited levels from doom2.wad, so no custom textures or scripts, just new level)