You're welcome to upload multiple tilesheets!
As long as they're all part of the same theme and work together to express what you want to create, you can submit them as one entry.
Participants can submit up to three entries per category.
>>And, is there a problem if, in my asset's page I include a link in case people want to commission me? Or would it be best to not put it?
No problem at all—you're free to include a commission link if you'd like!