Like BYOF, adding classic old frames would be a great addition. Also, there need to be more categories besides the three currently listed.
We do intend on expanding the categories eventually. Right now, as the site grows, we are focusing on the largest overall categories of bikes. Within those categories, the part lists can be tailored to further fit in to the different "niches" in cycling like gravel, monster cross, touring, etc. We hope to get to other categories like recumbents, tandems, BMX, and folding bikes down the road.
The BYOF idea would lend itself to adding classic frames and has been on the drawing board. It is a feature we would like to include, but we're still developing how it would be implemented on the site.