Signature Things
A few things to help out making a signature
first get a image host. I use
photobucket It's free and easy to use.
Now for a simple one image sig, simply in the signature section of your profile page, place
[img]image url[/img]
eg:
[IMG]http://img.photobucket.com/albums/g162/jack_zero/damon.jpg[/IMG]
would look like this

photobucket is very good in that they give you the whole image code underneath the preview of your picture so simply copy that and paste into your sig.
Now to have your image turn into a link so that when you click it, you can go to a certain page, then you need something like
[url=url of place to go][img]image url[/img][/url]
eg:
[url=http://www.gaiaonline.com/forum/guilds/index.php?page_mode=4&guild_id=377]
[IMG]http://img.photobucket.com/albums/g162/jack_zero/faith.jpg[/IMG][/url]
would be this

Right now on to random sigs.
A random sig is when you have something which everytime you refresha page a new image appears. Personally I use
Cut an Paste Scripts, but there are many others.
List of other Random Sig placesAnyway when you sign up, you can upload a number of images to that service, which in return will give you a html code to put in your sig, which looks something like
This thing doesn't get along too well with gaia, so instead you just take a part of that
all you need is the part after src=" ie for the above http://www.cutandpastescripts.com/cgi-bin/randomimages/randomimages.pl?username=demonpez
and place that in the image brackets like
so.
[img]http://www.cutandpastescripts.com/cgi-bin/randomimages/randomimages.pl?username=demonpez[/img]
thus giving you

you can combine that with the link method as described above.
[How To] Make an IMAGE MAP (couldn't be bothered to do my own as I don't use them but here it is anyway)