Here are some images of chess sets that inspire me. I can see all the possible design features, for example a multi-level chess board or abstract chess pieces.
The individual chess pieces must also look obvious to the player, If they become too abstract it will be hard to see what each piece is and where to position them on the board and how to move them.
A successful set in my opinion will have a big difference between each piece to help differentiate between pieces when playing. It should also be themed and have a set style that produces really interesting shaped pieces.
I also personally would like to create a chess board that is a little unique and different to any seen before with multilevels or shaped tiles. I think this is probably the best place to start making as it will influence the size and shape of the pieces. But first! to find a style/theme.