Great to hear, GigaLem!
For convenience, here's a general overview again of the things I've found:
- missing second exit in desert_md (--> the one shaped like in namida_desert / orig_marble, attached on the previous page)
- terrain piece alt9 from metal_md (attached on the previous page)
- various backgrounds from both the purple_md and the Freedom-Planet styles
- misplaced trigger area on the exit of sky_md