It is possible, but it will be a small picture since LoRa is made for and limited for low bandwith. How ‘much’ data you can send, depends on a few factors which are well explained by @arjanvanb in this post:
Why not say the limitations of LoRaWAN? Small bandwidth, extremely small bandwidth, and no pictures or such, just sensor data. And also actuator data, as switching things on and off. LoRaWAN is not Internet as such, it is small bandwidth in the extremes!
But it is useful and needed for applications within the scopes of the limitations. On, Off, what if, and a lot of important things you want to now, but no pictures and no sound, and no social interactions…
Also, if you have a large file that you split into many pieces, you would want some confirmation that each part has been received. That would need the gateway to confirm each uplink. But the gateway has the same limitations as nodes, but a gateway needs to share that limitations among many, many nodes, and also needs to use it for all kind of administrative tasks. So only a small fraction of the limits of a gateway can be used for your node.
In the fastest (LoRa) modulation scheme you can send approx. 11000 bps in packets of 250 bytes. The time on air is then 194.69 ms per packet. With the 30 seconds fair access policy of TTN this gives you the possibility to send 38522 bytes per day, which is equivalent to one 700x300 pixel jpeg image per day.
This is not a lot and I discourage the use of the network for these practices, so please reconsider.
So the question is indeed if you want to send such a small amount of data over the TTN network.
On SF7, one can send about 222 bytes each time, which then takes 368.90 ms and allows for only 81 such packets per day. So then it’s a 17,982 bytes image, assuming all packets are received well.
For SF12 it’s about 51 bytes per message, 2,793.47 ms, maximum 10 packets, hence 510 bytes.