What I mean is, this would replace every image. How would I know if there are new or different images in the new release? Is there a list somewhere that tells you what has been changed?
Otherwise I would be updating, but not updating any images that might be important.
Or are you saying there would never be any images in an update that are actually needed to be changed?
Part of the reason for asking is I used to do what you are suggesting with vBulletin or some other software, and sometimes in an update they would change the images,. e.g. from .gif to .png and so this method of keeping custom images safe from the update was sometimes more hassle than it was worth.
hence my question if I can just have a custom folder for Avatars, which it seems I can't. It has to be the whole lot.
Your choice though, create a custom style directory and occasionally upgrade changed images, or keep the default style directory and replace the default images with your custom images every time you upgrade.