The Slang Game teaches English…slang and idioms.
Here’s a game to test your knowledge of English animal idioms.
The Idiom Connection has written explanations of many idioms (though they’re not presented in the most accessible way). However, they do have a lot of good quizzes.
Idioms 4 You provides explanations of numerous English idioms. It provides them in various scenarios — all with audio support. Unfortunately, it doesn’t provide any visual clues, but I’m still adding it to this list.
ELT Pics is on The Best Online Sources For Images list already. I just discovered they have a great set of images related to Idioms.