The games I have worked on have been on my A1200 030/50, so I try to get them running at a decent speed on that. It all depends on the amount of colours, the size and amount of sprites on screen, and the size of the screen you use. Reducing the size of the screen increases the speed quite a bit, but still, Backbone is still pretty slow, due to being partially coded in Amos I guess.
The platform games always have to be push-scroll or auto-scroll. There's no flip screen option, although you can simulate this effect by setting your levels up in separate screen-size sections and placing a teleport event at each side of the screen, then making the player teleport to the start of the next screen. Just make sure all your rooms are above each other in the map editor or they will scroll sideways as you walk through them.
You can also make over-head viewed games like Chaos Engine and Alien Breed, although you have to be at the edge of the screen to push-scroll it, which means you hardly see the enemies coming.
If you download the package I've uploaded, you'll find a couple of games that weren't available on Aminet, as well as the standard example ones.
If anyone can hunt down Alastair Murray, I'd be happy to still pay for registration, but it would be even better if we can get the source code and continue development on the program.
Another thing I should have mentioned before, Backbone is great for making fan-games. Simply download a sprite and tile set from your favourite games (there are heaps of sites online with game graphic rips), remap them if need be, and load them into Backbone. Years ago, using AmiMasterGear to rip the sprites, I made a quick Sonic the Hedgehog game, just to see if it would work. The downside was the attack method, he couldn't spin around and kill enemies from any angle, only if he jumped on their heads. But it was still fun and simple to make. Other games, like Mario or Metal Slug might be easier to remake.