They both work. "From my trip" says that the photos were taken during the trip, but not necessarily about it. "Of my trip" says that the photos are about the trip. (I think this is the better one here, but again, both work there)

I read John's answer, which I also agree that the second sentence sounds better, but I will also help you with corrections. The first sentence should read, "I've enclosed some photos from my trip." The second sentence should read, "I've enclosed some photos of my trip."