Are the chessboard/chess pieces images free to use, or would that have legal issues with chess.com?
You should check with support:
https://support.chess.com/article/346-contact-us
But based on the user agreement, I'm guessing it's not allowed:
https://www.chess.com/legal/user-agreement
Any unauthorized reproduction, publication, further distribution or public exhibition of the materials provided on the Service, in whole or in part, is strictly prohibited.
Posting images of a gameboard composed on site, would probably be fine, but it would be safest to ask about your specific use case.
Are the chessboard/chess pieces images free to use, or would that have legal issues with chess.com?