Now i call upon the powers that be to help me find a new image to go by and i need your help
In all seriousness though, if ever I am looking for a new avatar picture or the like then DeviantArt is my first stop (
http://www.deviantart.com/). There are a huge number of seriously talented artists showcasing their work there, and a quick browse always turns up something that speaks to me. If you have something in mind then you can search for keywords, but whether through that or through random browsing I think you'll find something good.
Step two once you've located something is to drop an email to the artist. Let them know how much you enjoy their work, and ask if they would be ok with you using image X to create a forum avatar/signature. I've always received a positive response to this, but if they say no then respect that. It's the cool thing to do.
Step three is take your awesome paintshop skills and create a masterpiece. You can crop the image down to the part that you need, or go medieval on it and use every tool that photoshop/gimp provides to craft a masterpiece. This is the stage that I would recommend that you ask for help at if you think that you cannot fulfill your vision alone.
Don't be afraid to try doing this for yourself though. For something like an avatar photo it can be as simple as cropping a larger image down to just the part that you want:
For larger images you can just grab part of it to use, perhaps with some simple techniques applied to make it pop, but still very very simple.
...so, long story short. Find an image that you like, and play. Youtube is a hugely useful source of instructional videos. If you want a free but powerful image editor the try Gimp, if you want something that is user friendly and has the main tools that you will use without breaking the bank then Photoshop Elements is a good one to check out (I tend to use the latter, and switch to gimp if I need a tool that it doesn't provide).
Have fun.