Of course I understand that the learning process for toddlers and young children, especially when it comes to eating, is going to be experimental and often messy..... I'm sure doting parents, grandparents, aunts and uncles and others close to the child get a real kick out of this, if they're with the child at the time, and/or probably do enjoy photos and videos shared with them later if they weren't around when the kid first discovered the wonders of certain foods. Sharing this sort of image on Facebook with the far-flung family? Sure, why not go for it?
However..... it seems to me that things are a bit different when someone posts the same sort of family photos online on a public photography website which is seen by many others, most of whom are strangers to the family and to the child. There indeed, for various reasons, the reactions may not be the chuckles and the smiles. Some viewers may wonder why anyone, doting relative or not, would share a photo of a child which really IS unflattering.....regardless of why and how it happened, how funny it may have seemed to onlookers, or the age of the individual. IMHO food smeared all over someone's face, hands, clothing and the surrounding area is simply not attractive. I don't think I am alone in my thoughts about this.
It's certainly possible to post fun photos in which the child's dignity is preserved, showing him or her in a more flattering way. I've seen many delightful photos on here of people's children or grandchildren, photos which have been taken during some activity or during their wide-eyed exploration of the world....