My coworkers and I always struggle to draw iPhone frames on a white board that won't erase when we want to change whats on the screen. We've made prototypes that were too permanent (black electrical tape leaves a residue, oops) and too flimsy (paper cut outs of frames that rip apart when erased).
I recently started hunting for some frames that are stick-able to the whiteboard but also removable. I couldn't find anything within a reasonable price range, so I made my own. Finding printable window clings proved difficult, but the internet is a magical place. After purchasing a 5 pack of 8.5 x 11" sheets for $12, I experimented with the sizing to fit that frame, the correct way to load the printer, and voila!
Side note: Water will make the film sticky and peel off, so don't get the frames wet, but you can write on them with dry erase marker.