Hi there! Per the EULA:
4.1 The Product is not to be changed, altered or edited in any form. The User may make changes to the Product but only for usage within the User's personal projects, including games, media, and related projects. Redistributing and/or selling an edited version of the Product is strictly forbidden. Edits and alterations made to the Product cannot be the target of commissions, crowdfunding, and/or monetary gain.
You may edit the tiles but only for use in your own projects. They may not be distributed to anyone else.
Any other artists or commissioners must own a commercial license of the product in order to edit it.
Hope this helps!