yes, you can easily use a custom image. You just need to make it in the proper dimensions. If it is a two tile high door, you need to add an exclamation point to start of the file, like in the RTP and match it to the size of the door in the !Door3.png file from the RTP. You have to have a picture of the door in the down, left, right, and up positions in order to animate it in the game, also.drawing my own and importing it into the game