One way could be to put the last few additions right on the homepage along with the last few collab parts (both with thumbnails). I don't think a lot of people who casually look at sito know about the News Flash button or its utility is lost on them because since they don't have a sitoid they don't have the convient automatic culling.
Another thing thath might increase cross-traffic is making people able to list up to maybe 10 'favorite' other artists or art pieces on their Sitome page. This would be as much for generating traffic to their 'favorites' as for keeping track of people you like (there's been several times wvhen a particular artist caught my eye, but I didn't have a chance to bookmark him or I simply neglected to, or I wanted other people who look at my stuff to look at this guy's stuff because I love it, and I wished for a +fav button on the button bar). Your sitome could also list 'reverse favorites' - sitoids that have you listed as a favorite.