You could wait until the tape dries out. At that 
point, it can be easily discarded (with little 
risk of tearing the paper) and replaced with acid-
free tape. But since the paper usually yellows or 
stains under the tape as that happens, you might 
want to carefully try to remove it beforehand. 

For me, if the tape were on the back (or at least 
not *directly* over drawn areas) and the paper 
seemed sturdy enough, I would experiment with 
removing and replacing it before it yellows. The 
better the condition of the sketch, the more I'd 
be inclined attempt removing it in advance (to 
prevent damage).

But another question for sketch collectors: How 
do you store them? I have two *huge* sets (40-60 
pages) that are too big for even a few pockets in 
an Itoya book. Even smaller sets make it difficult
to turn the pages of the books without things 
sliding. For now, I've stored them in cut-scene 
bags, but I can't easily look at them like that. 
Keeping them one or two to a page in Itoyas would 
be great (and what I'm used to with my cels), but 
the expense woul