When I feel like it. For example, I decided to use this new (taken yesterday) picture of some wildflowers (and that answers the ‘what influences’ part of the Q) near my home town.
Very rarely do I change mine, unless I’ve made a comment about one of my animals. And only then, will use that photo so they are able to see whom or what I’m speaking about. Did that make sense?
Rarely on fluther, I may switch between this one and a photo of me once in a while but for now I’m okay. On other sites it entirely depends on how active I am and how I feel at the time :)
@Loser; Forgot to tell you that driving home today, I scared a Great Blue Heron from the pond that my neighbor and I share. He (Heron) was fishing… wading in the shallows on his delicate dancer’s legs. You might have enjoyed it