Can be anything. A reason 'why' would be helpful though.
I'll kick off with the four chaps below, who just happen to be cyclists. Why does it make me smile? I think they're just having a great time. And I'd like to be one of 'em. Four chums, (let's call them, from l-r, John, Paul, Ringo and Douglas) out for a ride up in the mountains.
"Time for a pose here chaps."
"Douglas!" says Ringo. "What are yer doing ya knob 'ead, yer posing like a girl!"
"Come on chaps, I've seen it in magazines. This is how the professionals do it" says Douglas.
Interesting frame on Ringo's bike methinks, and are those 'bits' sticking out on their forks for putting your feet on, and freewheeling?