well, I guess your question is about qualtrics, not scriptingrt,
right?
I don't think you could randomize the header logo, but I would just
leave the header empty, use an empty default layout, and then put
the images you want to use in a "static content-graphic" by
themselves (one for each), which you randomize depending on the
condition. for that, you use display logic, make it dependent on an
embedded data field, in which you store the condition. for a hint
how to do the embedded data field, see
http://reactiontimes.wordpress.com/2012/01/24/how-to-repeatedly-assigning-participants-to-different-conditions-in-qualtrics/
best,
t