I am not legal counsel, but i came across relevant information. Reproduction of copyrighted material is totally fine if it is considered Fair Use beneath the Fair utilize Doctrine. Th doctrine provides a litmus test as you are able to affect determine if your use could be considered fair. Below are the relevant conditions.
Rule 1 ... individual use is favored for reasonable use, while commercial usage is disfavored.
Unless you want to distribute these cards or sell them to your friends, you pass this test.
Rule 2 ... using imaginative works is much more more likely to need permission ...
You fail this test. The whole card is an innovative work.
Rule 3 ... only using a small portion of a copyrighted material guidelines towards reasonable use, while using huge portions shows a necessity for permission
This does not actually use. The guideline ended up being designed for books, flicks, music, etc.
Rule 4 Where a-work can be obtained for sale or license at an acceptable price, copying all or an important portion of the job (in lieu of purchasing or licensing an adequate wide range of "authorized" copies) would be unfair.
You fail this guideline, considering that the cards are offered for acquisition.
The guidelines are clearly vague, and various says apply them in a different way. Just Wizards can provide you satisfaction. All of that being stated, you might be safe publishing proxies because they are prohibited at tournaments, they have been useless anyhow, every person does it, and although Wizards strictly prohibits it, they've never ever gone after anybody for it.