A lot of questions are asked about what we mean by RTP. The intention is to use what comes with the RPG Maker engines, the things everyone has access to. If you got that file/asset/audio with your purchase of the engine (excluding bundled DLC's) Than it's usable.
Also, in order to facilitate use of any asset in any engine upscaling and downscaling images is allowed.
You may also make a map in the editor, screen shot it and use that as a battle background.
Finally, since the whole idea here is to push the boundaries with what you have, isolating images (such as one actor pose from a sprite sheet) and using that image in other ways like an icon to a sprite sheet, or an object to an animation is allowed.
What is NOT allowed is the modification/editing of assets to change their form or sound(with the exception of the in engine sound editor). Or the addition of custom assets outside those mentioned above.
Please feel free to ask for further clarification on this here. :)