Make your content fun for you and your clients! Uploading photos on your page is a great way to engage your clients by showing them your training style. This will also help you build trust with your clients and entice them to train with you.
Your photos should clearly feature you and have enough context to give your clients a good feel for who you are as a trainer. Show yourself demonstrating your favorite workout, take an action shot, or just smile for the camera. Most importantly, get creative with it and step out of your comfort zone, you've got this!
Videos
When creating videos, there's two main route you can take. One option is to talk directly to your clients through the camera (vlog style) and briefly explain who you are, what type of trainer you are, and what your expertise/certifications are in.
If you don't want to make an explanatory video, a video of you in action is also a great option! You can show your area(s) of expertise with example videos of how you run your training sessions. Either way, make sure your videos are engaging and focus on targeting the type of client you want to attract to your classes!