I got this error which was hard to find the reason for:
Image for slot [slot: neck, bone: root] not found: neck-02
But after doing some digging in the many skins i used, i found the skin that had the error. It would be useful if the skin could be shown in the error message.
Thanks! 
What version of Spine are you using? As far as I have confirmed with 4.1.17, the skin name should be after the ":" in that error message. For example, the error message in the following screenshot says there is a missing image for the backpack-pocket slot of the backpack-pocket skin in the boy folder:
Do you mean that you only got one error message but the image was actually missing in other skins?
The message after the colon is showing the path that wasn't found. It'll have the skin name only if you use a folder named for the skin. You could check Show all skin attachments then use the tree search to find it. We'll improve the message though, changing it to Image for attachment [xyz] not found: [path] so you see exactly what attachment caused the warning, which will also include the skin name, if any.
Oh wow. Sorry, I totally missed that! Thanks for pointing it out.
