Yep, that's pretty much it. You would probably want a fuse between the battery and the switch (closest to the battery is better) just in case you accidentally short something. It may not be necessary to take the return right back to the battery, the bike's frame may be connected to one side of the battery (I don't know, I don't work on bikes
).
It's probably best to take the power from a point that only provides power when the ignition is on. That way you won't get into trouble by flattening the battery if you leave it turned on. Alternatively, you could take the power from the headlight, which almost certainly goes off with the ignition -- it will eliminate the problem of finding a place for the switch.
What colour LEDs are you thinking about? Differnt colours have different requirements, so red vs blue require slightly different calculations for number of LEDs per string and value of resistor. Also consider how bright you want the LEDs. If you want to see them as bright points of light, you can use standard LEDs. If you want to direct them to the road and see an illuminated patch of road under the bike, then you'll need higher powered LEDs.
On a bike (or under any vehicle) you really have to consider mounting and protection of the devices. You don't want to leave exposed wires or places where debris from the road can break something.
