While I agree with the overall context, that people may very well spend money on family heirlooms (i.e. pictures), I don't see this as an investment by definition. Investments are stocks, real estate, 401k, IRA's... photography is just products and services.
Just because a purchase makes you feel good, doesn't make it an investment. I hired a plumber to perform services once... after he fixed the problem I felt better about the situation, but I'd never consider it an investment; nothing was gained, although worse situation was prevented.
My wife can go to the salon and have plenty of services done (hair, nails, makeup, etc)... she feels great after. However, my bank statement doesn't show any signs of 'investment'... actually just the opposite!