You can use html or forum code to put images in your sig.
It is not a good practice to link pictures from other people's sites as it is costing them bandwidth which costs them money. So if you can, you should have them uploaded somewhere that is your own place.
You have to have the picture uploaded to a server that allows hot linking of images.
http://ourworld.cs.com/ works.
(image)http://www.yoururl.com/yourpic.jpg(/image) but with square brackets [ ]. I used ( ) so that it would show up. The process is the same for gif's.
It should be the same as other forums so you could just copy and paste it if you have images in sigs from other forums.
The guideline for sig size is 10 lines of text.
So
____________
1
2
3
4
5
6
7
8
9
10
____________
Should only be around that size with text and pictures all together.
If you need more help, just post here again. I'll check up for you.
Your sig updates automatically and all recent posts should have the updated sigs.
If you check back here or refresh this page while you are trying your sig out, you should be able to see what you have done.
Or you could go and try it out in the testing forum.