Again, I don't have the editor up so I can test, but I'm pretty sure you can inject HTML right into the node text. For example:
TreeView1.SelectedNode.ChildNodes.Add(new TreeNode(@"<img alt="""" src=""testimage.jpg""> Here's a picture!"));
It seems to me that there is some kind of icon functionality available, but I can't exactly remember.
By the way, I learn all this stuff by Googling, experimenting, and using the MSDN. I would recommend becoming familiar with these resources if you want to be a developer. Forums are fine, but at this rate you're going to make slooooww progress.