That looks absolutely phenomenal! I like how the cards can still remain in the SGC holders, but the display only shows the black inserts.
The only thing I
might suggest is adding a small "Cracker Jack" or "Cracker Jack Ball Players" across the top or bottom of the display, printed in the exact font that's used on the cards. This may prove to be more costly than it is worth, and it's only a suggestion -- the piece looks great just the way it is.
This is what I was envisioning, fwiw....