What kind of graphics to use on the wiki pages is an interesting discussion. I think in general for wikis what I see is screenshots of elements in-game. However, one of my favorite sites RPGClassics often has perfectly cropped sprites with transparencies, and it’s glorious.
The good news is that either approach is easy for anyone to add! Screenshots can be taken and cropped easily of course, but all of the game’s pure, transparent assets are also online, for example: