Shredded paper is fine, but I'm curious... why just one corner? The only thing I have against shredded paper is that it gets DISGUSTING when they go to the bathroom on it. If you're talking about shredded paper like from an office, it doesn't absorb anything and it's going to make a huge mess, but shredded newspaper might be less gross.
The only thing I could see being an issue is if it's thinly shredded (again, like from an office shredder), you really wouldn't want to feed near that because it could stick to the mouse and accidentally be ingested.