It's possible to get photos of multiple users via Batch API https://learn.microsoft.com/en-us/graph/json-batching?context=graph%2Fapi%2F1.0&view=graph-rest-1.0
For E.g: POST https://graph.microsoft.com/v1.0/$batch
Request Body:
{
"requests": [
{
"url": "/users/abc@ssss .com/photos/48x48/$value",
"method": "GET",
"id": "1"
},
{
"url": "/users/xyz@ssss .com/photos/48x48/$value",
"method": "GET",
"id": "2"
}
]
}