You can describe a picture using the simple present if you like.
Printed captions under pictures or photos are often in the simple present to give a sense of immediacy to wherever is depicted. This is also true of newspaper headlines: Titanic sinks!
This is similar to the following uses of the simple present:
1 Giving a play-by-play description of a football match
Smith passes the ball to Jones, Jones heads it to Johnson, Johnson stops it, he kicks and scores!
2 Giving a demonstration, as on a cooking show
I take the chicken and dip it into the special sauce, then I place it in the cooking pan. I place the pan in the oven and let it cook for twenty minutes. While I wait, I chop some tomatoes...
3 Joke telling:
The past, present, and future walk into a bar. It was tense. (Joke from Fallout 4.) The joke apparently works better with the past simple in the second clause, if it works at all.
4 Story telling
There's this guy, you see. And he goes into the forest looking for his good pair of shoes, which he's been missing for a week. He comes upon this bear. Then he notices he's in between a mama bear and her bear cubs. He decides to...
5 Historical present
In 1492 Columbus comes upon a land he thinks is the East Indies. He sends out a landing party and the party meets the local natives, who don't look that much like Indians, yet the crew and their commander refer to them by this name.
6 Chapter titles or descriptions in an older book such as by Charles Dickens:
I I wake up to a knock at the door.
II The Earl comes home.
III We travel to meet Scrooger
You can use whatever tense is appropriate to describe the photo.
This was Bobby Joe when he was first learning to walk
But since the photo still shows the same scene now, in the present, you can refer to it with the present simple. This is like pointing to a picture and telling us what it depicts:
This is Bobby Joe when he is (or was) first learning to walk.