If I organize an event and I specify in the advertising that lunch / snacks are provided (but not itemized on the bill- one price), do I claim in meals or where?

Do not claim as meals, as this will only get you half of the expense.  Presumably the event was one you had customers attend, whether for a fee, or for the purpose of promoting and selling a product or service.  In this case you could include the cost of food as part of the event costs, or perhaps even as an advertising/promotion expense.

Where do I claim event costs. I'm an artist - is it in the same place as where I put art supplies?

Claim them as advertising.  Technically the expense is called advertising/promotion.  This expense would fit as promotion.

Thank you.