Place Reddit is an easy and exciting way to get varied pictures for your development/design needs.

Pick a subreddit ...
placereddit.com/r/unlikelyfriends/
... dimensions
placereddit.com/r/unlikelyfriends/100x75
...and random integer
placereddit.com/r/unlikelyfriends/100x75_17
Each number (1-20) gives a different image!