Link for "official" Wii game cases, as requested:

http://store.nintendo.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10001&storeId=10001&langId=-1&currency=USD&ignoreCrumbs=N&crumb1=&crumb1Ignore=&crumb2=%253CA%2BHREF%253D%2522javascript%253APassOn%2528%2527X%2527%252C%2B%2527ChooseView%2527%252C%2527%2527%252C%2B%2527%2527%2529%253B%2522%253EWii%253C%252FA%253E&crumb2Ignore=&crumb3=%253CA%2BHREF%253D%2522javascript%253APassOn%2528%2527C%2527%252C%2B%2527CategoryDisplay%2527%252C%252762707%2527%252C%2B%2527N%2527%2529%253B%2522%253EParts%2B%2526%2BAccessories%253C%252FA%253E&crumb3Ignore=&translateFrom=%C8%C9%C7&translateTo=EEC&usrSearchText=&searchText=&selSrchType=&page=&view=&productId=116705&categoryId=62707&lastAction=ProductDisplay&orderTotal=null&tranId=0&prevTranId=&jktranid=

EDIT:  This is the U.S. store, so only U.S. and Canadian orders are accepted.  I imagine there are similar stores in other regions. 

That's funny you mention that, I did that exact thing when I printed the Link's Crossbow and Wii Sports covers this morning.  

Instead of dvds, or wii cases, you can also try old ps2 covers as well. Except its going to have a black border around the cover art, instead of white. Looks kinda kewl actually and it fits pretty well with the link's crossbow training art; I just tried it with .hack//G.U. case and it works pretty well.

The only reason I used the Disney boxes was so I could keep all my Wii games in white boxes, all my games are in boxes with the "appropriate" color by system :)

I did think it was cool you could make PSX cases that fit in DVD sized boxes from that sight, I updated the one I still had that they made covers for as well. Odd that they let you make stickers for cartridge games, as well as duplicate boxart for those as well, not sure who is doing that.

Finally got the printer working. and everytime I try to print it, it has it on 2 pages. >_< How can I get the entire boxart onto one page. I've tried turning it sideways, but then for some reason it wants to print it on 4 pages. O_o

When it prints it on 2 pages, the cut off is right down the middle, right with the Wii and Link's Crossbow Training logo are. 

-_-

Open it in a graphics editing program and either double the resolution or shrink it by 50%. It should work then.

*E* Actually, wait... that probably wouldn't work right... if you really want to, go ahead and try it.  If it works, that's good, if not... oops?

How long is the download? And does it affect your Computer?

@I like Bacon:

If you open it in a program like IrfanView (freeware), you can just set the desired dimensions for the image to be printed in. A standard DVD case is 7.18" x 10.75".

@RCTjunkie:

It's just an image file, albeit a fairly large one.

My brother managed to get it to print on a single page. But the quality sucked so bad. I don't know what to set the printer setting to to make the quality better. I did set the quality to the highest, but it was more blurry. I don't know. -_-

I got them printed! They're awesome! :)