I love the custom cases and I used to be into doing similar things myself, but I found that I needed to reduce the amount of space that my collection takes up, instead of increasing it.
The best solution for me is the 'Ultimate Game Library' binders.
![](http://imageshack.us/a/img15/7337/walmart1o.jpg)
They hold 32 GBA games. They are
really tough to find now and usually demand a pretty penny on ebay, but I have two of them and they hold my entire GBA collection in about 5 inches of shelf space.
Coincidentally, I just watched this video last week and I like his solution (this is exactly how I store my GB and GBC games).
BTW, I love to talk about game storage and sometimes my posts about it are too long!