The second option seems optimal. You get to have control (you know exactly how much you give) and the customer gets a voucher with a fixed amount to spend. With most e-commerce websites that's more appealing than having a % discount, because users live the illusion that they already have the money and it would be a pity to 'waste' them.
The idea is nice, but you need to sell it better. Many painters work from pictures, that's not very new.
How do you go about hunting for new pictures to be painted? You could have a story here.
Or maybe paint extremely famous photographs, that could also be catchy.
Hi! They won't see your name as long as you don't put it out there. Google other fresh LLC and see if there are websites fetching information about the business owners.
Try also putting your name on google alerts, you'll be the first to know if your name pops up anywhere on the internet.