Firstly. welcome to the Guild, The Mappiest Place on the Web

Secondly, if you are using Paint.Net, you should look for tutorials by PeaceHeather. She hasn't been on here for a while now, but she did post a few real nice tuts for PdN. In fact even browsing the tutorials or WIP (Work In Progress) forums can expand your knowledge base and give you ideas to try with your weapon of choice.

Have fun and enjoy the ride. Post anything you come up with if you want pointers or have questions. We are not judgmental at all and can be real helpful if you but ask for it