If you don't have full set to sell, you are not announcing full set (you could write doom set w/o helm) and / or not adding wtv else helmet to your sale shop.
Saying Doom set means full set of all doom parts, which it wasn't in your case.
You should read server rules to know that it's forbidden.
You can contact support and get unbanned just with the warning this time.
The people, whos pics you added, are different story, and you should understand that. They are not replacing items with similar etc.
Spammers are also not allowed and are being banned all the time.