The thing about Nicktoons is that the name implies original Nicktoons so there is room for the other new cartoons automatically. (Not that I wouldn't rather see the old, classic Nicktoons that I grew up with, but that's beside the point.)
Boomerang's name, on the other hand seems to me to invoke a relation to the baby boomers generation. I would expect to see more cartoons that people grew up with in the 50s and 60s first and foremost. Then, perhaps, a few cartoons from the 70s (and stretching it) the 80s. Realistically, I get that this may not be such a popular market to just show cartoons from such a narrow time period. Of course they would need to expand their programing some, though now I feel as though they are in the first stages of using Boomerang as a dumping ground for CN's more recent discontinued series. Mind you, it's not a big deal... yet. I just feel as though eventually it could get out of hand. Let me reiterate that I love seeing Justice League and Dexter's Lab. I'm just not quite sure if Boomerang is the place for that.
By naming logic, you could say that TV Land could be open to all things television... But it was not originally branded and marketed that way. It started as a network to show classic television and it worked towards that goal. Now, it often seems as though it is working against it. Going against a brand seems to be a good way to loose viewership if you ask me.