Here's some from diamondus:

Tiles 1,2 and 7,7 are exactly the same
Pointless tile 1,19
Cave spikes have the background from the old 1997 diamondus
No opposite version of tile 8,40
Pointless tiles under the top half of textured BG
Tiles around background trees that aren't needed
Diagonals at the bottom of the set don't join to the main tiles

There are probably more but these are the ones I could find.