There's a lot said about the graphics, so I don't want to add anything much there except to mention that the improved graphics on the 'ovine' re-implementation of Imogen bring the game up to date without otherwise blunting its look or feel. That's the sort of thing I'd hope to see in these reimplementations. That said, Ovine's Imogen is 8.4M which seems a little excessive for what was essentially a MODE 1 BBC game
To be honest, the graphics never bothered me anyhow; the thing that set Repton out from the rest initially were the puzzles. They can't be lost, obviously (although timing was important on parts of Repton 2 IIRC, which was tricky). Repton 2 had its huge scale to bring in to the mix, and Repton 3 brought the map and graphic editors which really paid off with the extra levels that Superior released. No mentions was made of an editor - are we just using Paint and a text file ?