Personally I dislike it when a company or individual sells something like this for a price similar to commercial sware regardless of their claimed right to do so. I must say though that you cant really criticise someone charging a reasonable fee for this like in that ebay ad so long as the apropriate licences are made clear and retained. Also they can use images from the game itself. If they are including add-ons not released under the same license or one which similarly allows said distribution, that would be an issue.
In practice who would pursue the legal issue?
You would have to have cause and means which effectively eliminates most proponents.
If the said company or individual is however misrepresenting something, such as presenting it as their own software, then just about anyone could make a complaint to the appropriate government agency dealing with trading standards, keeping in mind the jurusdiction implied by the location of the sale/advert.
If you dont want companies to use your creations issue them under different terms.
As the creator the t/c are completely up to you.
If they ignored it you could put them in a bad situation then of having to withdraw their products.