Frankly, one would think if they cared enough about other people using their artwork, they would've said something rather than years later after the image was used. They had uploaded the image to the public internet (likely on a site that thousands of people use daily such as deviantart and without a watermark), so I wouldn't be surprised that someone scooped up the image to use it for a roleplay.

That being said, I have found a number of artists that I personally have taken a liking too from people using their images. Some have been from this site, some have been from elsewhere. As Nutts put it:

[quote=@NuttsnBolts]
Secondly, shouldn't someone be proud that an image was theirs was shared? You wouldn't see the same hate on Pinterest, you wouldn't see the same hate on Tumblr, so why a nobody writing forum? As I said, it's not being sold, it's not being claimed, the person is "admiring" the image enough to write a story about it, and their only mistake was maybe that they found the image on Google image search.
[/quote]

Personally, I struggle to see why someone would upload an image to the internet, most likely for exposure, and then complain about someone exposed to it for using it in a roleplay on a roleplay forum (especially if they didn't take the necessary precautions to protect their work before uploading it if it mattered that much), but yeah. Anyway, outside of any legality or copyright issue, and as long as they're not claiming it (or using it for commercial use e.g. selling the image), I don't see any issues with someone using the image.