Room treatment questions.

I'm setting up a 2 channel system in my den and want to do a little room treatment if it will help. The room is carpeted, about 18'X18' at most with double swinging entry doors on one side and a large window with wooded blinds on the other side. The door opening sidewall angles out so that the front wall is longer than the back wall so there will be extra space beside the right speaker. I'd say the ceiling is about 12' feet or so with a ceiling fan hanging from it. My speakers will be monitors (no sub yet) and sit on stands on both sides of a 60" desk/table. I'm going to have at least 3' on both sides of them (more on the right) with at least 2' behind them to the walls. I'll have the speaker fronts far enough from the back wall that hopefully the desk won't cause bad problems. Right now there are just some various pictures hanging up, a few plants, my golf clubs in one corner and an 18"x18"x74" wire shelve/tower in another corner. Also, I have a small laptop table in front of the window (on the side). I don't want to go overboard and hang panels, etc. everywhere but am looking for some things that I can do to make the room sonically better. Maybe hanging plants in the corners, corner tubes, small panels etc.. It's not the perfect room because of the big double door/angled wall opening into another large room on one side but I'd like to do something within reason to help out my sound.

Thanks for any input.