I have similar problem, but just with c*stom item display icons (?). So, yes I know that this is a really really old problem with the c*stom items, I've done some reading, but still couldn't find a way to "force" the client display real icons rather then "?" in character's inventory and bank. And no, I do not want to "fix" this by installing some addons - I want to fix it from the root.
So what I tried is bit hacky - to edit .dbc item files like my custom item is already in the .dbc, (like any other "official item", which is created by B******)
So this is what I did while using MaNGOS 9200, no custom patches, UDB (DB for 3.2.2 client):
1) I made my custom item with ID entry 52063 in the item_template in my sql DB
2) Opened It*m.dbc and created a new entry at the bottom with entry 52063 (on client 3.3 in It*m.dbc the greatest item ID is 52062, so the next one would be my custom item (a+1)).
3) For display values of my "new custom item" in It*m.dbc I copy/pasted display ID 1399, which was already used by other "retail items", which do not show like "?".
After this procedure I still can't get rid of that "?" mark. Correct me if I'm wrong, but basically I think that, the "realm display info" is hold in ItemDisplayInfo.dbc, and by creating a n*w item entry in Item.dbc and pointing it's values to already existing "retail" display info" in ItemDisplayInfo.dbc should produce a result like if the item was created by B*******.
I think that it's not working, because probably there are some more .dbc relations with other .dbc files, which I still don't know about.
Please - if somebody has a already a fix for this custom item "?" icon display issue, do not hesitate to post here, or if the fix requires client/client file mod*f*cation on PM ( for obvious reasons )
To the "copyright lawyers": I dared to edit the .dbc files only for my very personal, educational, non-commercial purpose. I don't support the non-educational modifying of the client and it's files.