Motorcycle batteries are just lead acid batteries with a nominal 12V output. When completely charged, they can be higher than 12V and when running out of juice, can be below 12V. You can regulate almost any voltage you want (less than 12V) using linear regulators or for higher power options that require a regulated 12V or higher supply, you can use a buck-boost converter.
The battery is capable of delivering several hundred amps so you must design in proper safety measures to ensure you don't destroy it. Excessive current draw can cause the electrolyte to boil giving off hydrogen gas. If the battery is sealed, the presure can cause the case to crack spilling sulfuric acid on everything near it (not good for the skin). The hydrogen gas could also combust causing a number of issues that aren't good for anything in its immediate environment.
Just make sure to put fuses in all your circuits off of the battery and you should be all set.