you'll have display issues, partly because the two center pieces are long and skinny, it will look odd as a thumb, either small or fuzzy. you would have to really scan these or get very good images of it then upload like normal. but telling the buyer they all go together at different heights will be the hard part.
In short I don't think there is a way to sell it as one piece. You could just upload and number each piece, and make sure people understand they are part of a multi piece painting. Then maybe link the other pieces in the description. I am not sure how accurately they will line up, or how color consistency would work if one or more of the pieces happens to be printed on a different printer. It's a good question, and it has crossed my mind before.
it would be hard. you may sell one as an abstract, getting people to understand they need to buy and ship 4 pieces may not be easy. and trying to figure out the amount of space it took would be hard. and framed would look strange.
