I think the idea of no links in the first few posts is just fine.
Maybe some warning before users get locked out on their 5th post?
Photos, on the other hand, are an important part of the forum. So many "mechanics" issues are best served with photos. For example, determining the difference between freewheels and freehubs, looking at wear, chain routing, etc.
Bike appraisals?
Does the old method of loading photos as attachments still work for newbies? It is a little counter-intuitive of a system, but had worked for them in the past.