I just created one and I would like to put it in.

first you have to upload that pic somewhere, eg Drunk duck extra files. So you click on the little yellow "i" next to one of your comics, then click on "Manage Extra Files", upload the pic and once uploaded copy its link from the list (right click over it, "copy link location" ).

Then, you have to use BBCode in your sig to show that image:
Edit your signature, paste the url or 'link location' you copied before and write

be sure to write all without spaces

Thank you! That is very helpfull.

so, where's your pic? =D

If you also want to make it clickeable, read this first, and instead of "here" put the whole image code