Here is a thread
where changes have been made to the game graphics to correct some problems encountered.
Certainly some files won't be needed as they fix display priority issues in different castles and I haven't started testing fheroes2 yet.
All the changes made are indicated in the changelog.
Some of these files have been modified by Uhm, try contacting him on this site to see if it is possible to use some of his modifications for your project.
For the modifications made by me, it's okay.
Is the list of sprites to modify for your project available somewhere?