Revert "Fix the background color"

This reverts commit 379dc02d39ed796c65a6fc827ace6e68a30b6d5c.
Revert "style: mach bg colour with main banner"

This reverts commit bf368650a81b7582416b8b38d1fedc940f681cb9.
Fixed banner art

This time, it's permanent. Modded the PNGs to be transparent so they
look good no matter what (dark) color.