Building a New Cage... Suggestions?

I am finally, after way too many years, upgrading Pikachu's cage. I have a Ferret Nation cage and I'm planning to take all of the ledges and shelves that came with it out and making everything I possibly can out of Pine. I want to fill it with toys and things to entertain him, but outside of the normal twigs and hanging things, I'm not sure what to put. Not only does he destroy everything I put in there very quickly, he will get over certain toys very fast if I buy them in bulk. Anything hanging will be in pieces within a day. And I have a saucer wheel for him which he only uses as a second bathroom.

What type of toys, entertainment, misc. items should I include?

I'm making a hay holder, litter box, house, and trying a different wheel.

Also, I'm doing it Mario themed. :)