My friend has promised to draw me a few times and has yet to do so. I'm upset.
Has he promised several times before?
Yes, a few times in front of a group of my friends.
It's not really your place to demand things in case case, as your friend would be going out of their way and the drawing is essentially a gift for you that they're doing free of charge.
I just want my drawing, he's been making excuses.
I get that you want the drawing as it would be a very cool thing to have, but you need to be patient. I'm sure your friend hasn't forgotten, rather they're dealing with other priorities at the moment.