Dislike button - seriously dislike that suggestion
Photo sizes - meh
Private Threads - This has merit - I have moderated on other sites where the thread starter can actually moderate posts of other users at his/her discretion.......
Look and feel - No doubt the green shades and set up here is in need of an update. Theme, Templates and skins could all be upgraded and look better
DualCore here looks OK
I like the look of Ravio and Tiaw as well but I am unsure of the functionality or the amount of effort to maintain the site using that phpbb.
Fun times for whoever does this for you. Look forward to whatever it is.