Do you tip the photographer doing a family portrait?

I won a family portrait through a contest/giveaway and put a $300 refundable deposit to hold our portrait date. I wanted to let the photographer keep the $300 as a tip, especially since I’m getting this done for free. Is that a nice gesture or is it possibly tacky/insulting? Is it enough?

TIA

Edit: it’s a photograph they take and then paint (fine art). They said it is worth $2,500, that was my reason for such a big tip. Should I still tip less than the $300?