Today I spent a long time drawing a forest background. It's not amazing even after a couple of hours' effort. Working at high dpi means there isn't really enough detail in this, and I don't have the time to get it there. But at least it's thematic.
I was thinking of trying to tie gameplay elements into the background. After all, both the level layout and artwork is in Inkscape. I have this working a bit - like this custom rock at the bottom left that you can stand on. Maybe I'll make use of this technique in the level design, but this would require an investment in graphics for every level, and though I might get a bit of re-use I probably don't have the time to do it justice.
Here's a video: https://www.youtube.com/watch?v=4t78svjl7Mw