How to add a picture in forums, signature, or private messages ?

Images: Use the Tags [ img] and [ /img] (with no spaces in them).

Signature: You already seem to know how, seeing that you have "make it happin captin" in yours, and same code can be used for signatures to insert images (but written manually).

Private Messages: Again, same code can be used to insert images, GIFs, ect.
Note - Different than PR's, those are the ones texted back and forth in game, and of course they can not have any sort of code.

For more information about the forums (how to do stuff), click on this link: http://atwar-game.com/forum/topic.php?topic_id=23596