I started uploading a bunch of item icons extracted directly from the 3DS game files.
Unfortunately the picture files are stored rotated 90 degrees to the right, so I had to manually flip them 90 degrees to the left.
Also some icons are very confusing, particular salted/grilled fish recipes and also several of the juices/smoothies.
There is a little bit of logic involved with the way files are organized but the filenames aren't item-specific. For example, oven recipes are named I_CookB##_##, while medicine are named I_Drug##_##. The numbers aren't in order of difficulty or sorted alphabetically.
I will do my best to name the files appropriately, but there will be likely some mistakes.