I guess that Board 11 will still support capsule images. If not, it's just something to plan for. My question is:
do the images get loaded each time they are requested or are they cached by the browser?
It looks like Board gets your background image with something like this.
This line gets my Tools.jpg
So you won't find your image name in the list of assets the browser downloads, but you will find the hash.
If I clear my browser cache, the headers for the hash image state
Status Code: 200
If I reload the page I get
Status Code: 200 (from disk cache) or Status Code: 200 (from memory cache)
So yes, your images are loaded from the cache.
Retrieving data ...