I don't think it was intentional, Travis' roommate had a Sony camera that was found inside Travis' BMW (late March '08, I think, before she left for Yreka), I think it's possible she took the nudes of herself with Zach's camera, took the memory stick and left the camera in the BMW. On murder day she used that stick in Travis' camera (as Sony's only use Sony sticks), thinking she had already deleted the nudes off it so it was safe to use. According to Melendez there were 90-some other pics on that stick, undeleted, we don't have any idea of their timestamps or who was in them, Travis hadn't had his camera very long, and as far as I know, JA hadn't owned a Sony.
I don't believe she meant to leave evidence of her being there, can't even imagine why she left the stick or the camera there (washed or not), the pics were evidence that someone was taking pics of him while he was showering, sure she thought the washer would scrub them but why chance that? Who else took pics of everyone, everywhere as she was known to?