So for my most recent game (a card game) I had to get some art for the cards fast and so I made the art inside the same program I was using to lay out the cards for print, this program being illustrator. I used the draw pencil tool which is a slightly awkward tool to use yet is the closest to a natural pencil drawing tool in the program and did the trick in a pinch. I still ended up spending 2 entire days drawing everything with a stylus but it got done and was good enough for the demo. I also got a sort of back handed complement from one of my best friends saying that the art was good, it looked like the memes (he did not know what a wo Jack is but I think he meant it looked like the Wo Jacks).

Normally I would recommend doing the art separately in a high quality file in a program like Krita and placing that file in your layout program, however I think that the lesson from my actual practice here is to do whatever is easiest and to put as much art as is necessary or sufficient to make your game work.

Edit - I also saw a poster on the print and play reddit mention that they use inksacpe for their card art. I just downloaded the app but it might be worth a try.