Like some other people, I still own the retail disc of MDK, but not the box nor manual. I am currently working on a project that is essentially custom box art for it.
It is actually modified version of the custom box art found in this thread: http://www.gog.com/en/forum/general/uno ... ames/post1
I am modifying it to better suit people who do not own the GOG version of MDK. I am also going to resize the manual to fit in a modern DVD case. I will post both of these on here when done so people can use them.
To do this you will need blank DVD cases, which can be bought at any hardware store, and some precisely sized paper to fit the manual for a DVD case. You will also need a special type of paper used for DVD covers, which can also be bought at a hardware store (preferably Staples).

Here it is (I know it looks rough but when you print it out it looks a lot better): <taken down>
Resizing it is up to you, I can't remember the dimensions, but it will not fit on the DVD case as is.
EDIT: I am currently attempting to fix the shitty looking edges.

Alright! I have fixed it and it looks much better!
http://img403.imageshack.us/i/mdkboxartfinal.jpg/
Enjoy!

Wow, this looks pretty cool.