You can make your own tarot out of any media you wish and size or shape(though consider practical applications of the tarot), if you are not to good with drawing or painting try a collage or something similar.
I also suggestion you meditate on each and everyone on of the cards and explore the meanings of each in depth, before you start your deck so your understandings of them are sufficient. Also you can design your deck around themes or something which is important to you.
Its quite the task to design 78 cards but it is well worth the time and effort. Best of luck with your endeavor.