Well done!
Looks like Dumyat's gave you that bug as well!
Schiehallion is great hill, steeped in history and myth. The boulders will give you something different and if you carry yourself off to Kinlochrannoch after/before you get your photos of Schiehallion's famous pyramidal shape.
Lawers, however, is the 10th highest mountain in Scotland. Has a high start and on the way you'll bag Beinn Ghlas too. Two for the price of one with some grand views of Loch Tay and a handful of other Munros.
Ben Lomond isn't too tough either, it was my first one and has commanding views of Loch Lomond and The Arrochar Alps.
Your choice though fella, enjoy whichever one you pick!