I can't find this in any dictionary, but it seems to mean something like picture. Is that right?
I don't have an example sentence, because that word was the whole sentence.
I think it comes from 撮影【さつえい】 where つ becomes ちゅ for some reason (slang?). A bit like おやちゅみなさい.
Seems to me that さちゅえい refers to 撮影会 events. There are many types of 撮影会 but the main ones are for amateur photographers to meet, to take a picture with a character or model, to create publicity with an open photoshoot, or to recruit new models. They are discussed in more detail on Wikipedia.