The images are not always the full stack images (the c image) - for example, medicine just uses the a image, and there are some other exceptions. When changing the pages images, make sure you use the correct one.
Ideally, we also don't want to have duplicate files (its harder to maintain, its harder to know which image to use when etc). Its not really an issue if the image name isn't the same as the page, because once the image is set as the page property we can call the image by calling the page image (e.g. with Template: Icon Small or with Template: Q or Template: P). This is better than specifically calling the image because you can just update the infobox and all the images everywhere on the wiki will update too.
That we don't have a colored version of the correct insect meat stack size image is a bit annoying though.