Since so many people asked for support to upload documents as well, I have implemented this functionality into my WikiWebpart. Now you can add pictures and files directly into your wiki by uploading them from the clients.
As always, you have to install the solution, and activate the WikiWebpart feature for you Sitecollection as described in Updated WikiWebpart + Tool to install it.
The Webpart will detect an existing picture and document library, and use it. If you have multiple libraries on your website, you can configure which one to use in the Webpart properties.
Note: This version of the Webpart will install itself into the GAC.