How do I change the buddy and invisible symbol?

[calorie]

Untested, but in both the forumdisplay_loggedinuser and forumhome_loggedinuser templates find:

$loggedin[invisiblemark]$loggedin[buddymark]

And replace with the following:

<if condition="$loggedin[invisiblemark]"><img src="http://www.domain.com/forum/images/misc/whatever1.gif" alt="" border="0" /></if><if condition="$loggedin[buddymark]"><img src="http://www.domain.com/forum/images/misc/whatever2.gif" alt="" border="0" /></if>