Linkbucks is not that bad considering that you can always skip the waiting time but I doubt that the income will be any big.
I think it would be cool to leave all ads the way they are because there's not too much of them at the moment and introduce a donation system. Actually if everything was free and there was a donation system instead of VIP (with a list of those who donated with an option to be anonymous) it could be a nice solution.
Sometimes people pay more when they don't feel any pressure to pay, just to support the site to make it work fine and evolve.
Creating a system that would work that way - convincing people that they will be so nice and generous and that they can support development of a site that they like and enjoy might be an option worth experimenting with. It works for some community boards.