User:Tiddlywinks/Missing Dream World item artwork
If you have an account on the PGL with a game synced to it, you can see the GTS trades you've done on there, and the trade summaries include "Dream World" artwork of held items. I looked at a:Category:Pokémon Dream World items and compared that to the List of items by index number (Generation VI) (excluding Key items and TMs/HMs) to come up with a list of items that should be tradeable and are missing "Dream World" artwork.
Getting artwork
"Manipulating" the GTS
There's a few ways you could manipulate the GTS to see the artwork on the PGL. The easy options are to actually do trades. Either trade with a friend (in this case, both Pokemon could hold items you want to see artwork of), or, if you have two games, you can trade with yourself over the GTS. In the latter case, in one game, just put up a Pokemon people aren't likely to be terribly interested in, then quickly switch to your other game and "Seek" that Pokemon on the GTS (it should be one of the first ones returned, and you can double-check the player name and location) and trade a Pokemon holding an item you want to see artwork of for it. That way, in the worst case scenario that someone else trades for the Pokemon you deposited before you can get to it, you haven't really lost anything (and you can even just restart with the Pokemon they traded to you). The advantage to doing an actual trade like this is that the PGL will keep a record of all of these trades (so long as you've synced your game to your account before doing the trade), so you can harvest pictures at your leisure.
The other option for manipulating the GTS is to put up a Pokemon holding an item you want to see the artwork of for deposit and then ask for an impossible Pokemon (like lv 1 Zygarde). The PGL website also shows which Pokemon you currently have deposited for trade on the GTS, so you'll be able to see your deposited Pokemon and the item it's holding. The disadvantage of this method is that you have to grab one item's image before you can reclaim your Pokemon from the GTS and start over with another item. The advantage is that you only need one game.
Saving images
If you're willing to make your Profile public or semi-public (you can set privacy differently for individual pages of the Profile if you want) and give me the link to the GTS page of your profile, I'd be happy to grab images of artwork. Probably there are other users around (who may be paying attention) who can do the same service. Otherwise, I only know how to explain how to find images using Firefox. I don't know if other browser will be able to do anything similar.
The easiest way to find an image on a page in Firefox is to open the Context Menu (right-click) and click "View Page Info" (or, in the Tools menu, just "Page Info"; or simply press Ctrl+I). At the top of the window that opens, click on the icon labeled "Media", and then browse the list on that page until you find the image for the item you're looking for.
A slightly more targeted option which may be of use and may extrapolate to other browsers: if you highlight text/part of a page and right-click, there will be an option, "View Selection Source". The way the PGL is coded, viewing the source code for the whole page probably won't be very useful most of the time, but with "View Selection Source", you should be able to look for image files in the source code. You just need to make sure your selection includes the item image. Alternatively, the "Inspect Element" option in the context menu (no selection necessary, just right-click on the image) in Firefox, Opera, and possibly Chrome may function slightly differently in presentation but still allows you to see the address for the image.
Items missing artwork
Nothing else, it seems. (As far as non-Key and non-TM/HM items go, anyway.)
Previous generations
These are items from previous generations - inaccessible in the current generation - that don't have any DW/PGL art.
Feel free to add anything you want to this list. I don't know that I'll be bothering with it at all myself, but if other people think it's worthwhile to note something here, then go ahead.
- Gen IV mulches (Damp, Stable, Growth, Gooey)