The palette could be more optimized. Colors 16 and 17 could be put in 0D, 0E or 0F, freeing palette row 1. Also, as per the Palette Preferences v2.1 diagram, palette row 5 is the preferable one to sacrifice, so I'd remap the colors currently in 7 to 5, the ones currently in 5 to 4, and the ones currently in 4 to 7. With that, there'd be 3 colors overwriting the vanilla dark blue colors in row 7, two of which I'd remap to colors 73 and 74 (red triangle colors) and, lastly, the final color I'd remap to the back area color, which was not used in this submission.
This guideline wasn't followed:
Originally posted by Background-specific Submission Guideline
Your background should have the best scrolling settings possible in the sample level.