This would be one area in our home that we struggle with a lot. We live in a modest size home, the rooms are not large and we do not have an extra room for a playroom. Couple that with two kids that have too many toys, and you've got a mess! Our t.v. room has become a playroom, because it's where the majority of toys are stored. Both kids have toys in their room and then several big sets of toys in the t.v. room.
The things we have done to up the storage are to have the Hubs' dad build some shelving with storage cupboards and a lego table I recently picked up at a garage sale (score!). It was a drive-by find, we were on our way to the grocery store.
This room gets horribly messy, especially when the kids have had a whole day in there, which has been a lot lately with all of the rain we've been getting. A new goal we've tried (try being the operative word) to maintain is having the kids pick up their messes a few times throughout the day, so that the toys don't go knee-deep! I've also weeded out toys a few times a year so that things they don't really play with or that they've outgrown get passed on to someone who would use them.
My biggest challenge recently has been to instill some good habits into my children. With a 4-year old and a 2-year old, it can be like having two tornadoes in the house 'round the clock. We are trying to teach them that they are responsible for their own messes. If anyone has tips or tricks on how to make this work, let me know!