I think you should start with your business structure.
What best suits your business then you will be able to find out
what write offs are available to you.

As for registering your name think of it this way if you spend alot of money advertising your business you want your brand to stand out
so registering is very advantagious for you.

What do you mean by selling pictures online?
Please tell a little more about what your wanting to do?
Best Regards
John