Freaking awesome!
Answering your question about size, I do think it is important to give creators as much control as possible, or at least most of the time. So I would be in support of not only increasing the resolution, but also being able to export or work with multiple resolutions, aka being able to choose.
However, I can understand there being a bit of a technical limitation since you're just working on your free time, and it would take a while to implement support for multiple resolutions. As it stands now, I think the current resolution is fine, it works well for icons as well as for the types of games I play around with making, but I would like to see if it could be pushed to 256 by 256, which could be used for some pixel art cut scenes. If I remembered you system worked well for pixel art.