I've never seen an illustrated dictionary on the Internet, dale. But I think the words and concepts which are usually illustrated in such dictionaries (animals, architectural terms, plants, etc.) will have an entry on Wikipedia.

However, this thing is replete with the kinds of etchings found in old illustrated dictionaries if for whatever reason that's what you're after—though it's pretty sparse as a reference tool.

Here, for example, is the illustration for Acteon.