Others have given good alternatives but the problem isn’t that you have two sentences, but rather that you use the word ‘reference’. Without context, the idea of a ‘reference photo’ doesn’t mean anything. If the photos really are a reference for something, (which is unclear) you need to give more details and use the appropriate articles. For example, The reference photos used to identify the attendees at the event are attached. Alternately you may mean something like ‘the photos previously referred to’. You could say that explicitly but probably don’t have to because it would be clear from the context. When we last spoke, I promised to send you photos of the property. Please find them attached. (I’m obviously referring to those)

Make the life simpler: The photos are attached. there is no real need to explain you are shaing the photos because when a person gets an email with the attachment it's obvious the content of the attachment is being shared it's like you are writing "Here, I give you an apple so that you could eat it with your mouth" -- it's unlikely a person will stuff it into the ear, right?

You could say "I'm attaching reference photos", or "Please find the reference photos attached", or "Reference photos are attached".

I would normally write the following: Please find attached documents/ photos as discussed/requested.