[zeroimpl]

It does seem odd that browsers don’t preload images for hover effects. I guess in practice most hover effects just use colors? Otherwise there’d be a noticeable lag the first time you hover or something.

[iMerNibor]

This is actually an issue, to work around this as a dev you would usually use sprite sheets (one single image file with multiple images in it)

[hombre_fatal]

You can front load it with an <img> tag and various other ways. Look at how arbitrary asset loaders work for browser games.