when you say "hi res C64", you mean "one BG color and one FG color per 8x8 tile", right ?
I do not spot flaws, but you could clearly benefit from more "sand-to-water" transition tiles (e.g. rounded dither rather than just blocks of dither) ... Unless you're already reaching the 256 caracters limit, of course
I know I broke them for the robots (done on purpose)
You've got a friend working on a 4-bit sprites enhancement to the VIC ?