Sorry, I have not had time to look into this for the Linux version. I want to try and update the game before February though so that it matches the Steam version, and I'll try to see if I can remedy this issue.
As for the background, I'm aware. I was excited to get 3D backgrounds working at all, but didn't take the important time to polish them and make them more cohesive with the rest of the game. This is something I'd like to fix in the future but am unsure if / when I'll be able to.
Sorry again for the delay.