Hey, welcome to the guild!
I guess, for tradition, I am supposed to say the following "We're the mappiest place on the web!"
Your first map looks nice so far. I don't use computer programs yet, so I won't advise you on the desert, but I can say your mountains look a little "plopped down". In other words, it doesn't flow with the extremely flat terrain next to it. I'd suggest adding some little hills/ripples on all of the land to give it a more natural look.