Celebrating the Milestones -- then maybe you could do something cute with stones. Maybe you could do a picture filled with stones - and have 1st Anniversary on one - 30th birthday on another.
There are a lot of play on words that you could do with stones, pebbles, quarry.
The stone on your finger
The rock your hubby is for you; your birthstone; join us for drinks on the rocks
thankful for rock-solid friends.
Or play off the Rock - in rock 'n roll
You could do little favors with the rocks that are engraved with words or those worry stones - or just have them set out as part of the decor
Ok, maybe you're not into rocks
Do you want the party to have a certain theme? I find things get a lot easier if you first have a theme and then can build around that. I love planning parties, and I usually start with the theme or go to a party store and look around and then get an idea playing off a fun napkin or decoration