I discovered a project someone made a couple years ago and we never heard about it. It's quite a remarkable project. It uses multiple
non-overlapping layers (side-by-side) for background graphics, leaving empty areas of the map that have no playable area (by not putting a layer there), and one Main layer covers all of them to provide the foreground elements and sprites. It's all hand-drawn pencil graphics. It's a pretty complete game - can take almost an hour to play. And it has a variety of enemies. There may be bigger projects in the works (independent of this one), but I was surprised to see a project of such quality from so long ago that I had never heard of! Take a look at
The Adventures of the Overgrown Oatmeal on the SGDK2 project listing. It's a 43 MB 7-zip file containing an SGDK2 project for SGDK 2.1.3. Let me know if you have any trouble with it. I had to do some strange things to get it posted since I couldn't seem to upload a file of that size the normal way. Thanks to Chris Clarke, the author of this project!