What is the best way to include external photos or video in my followup messages?

The actual text should always make up the majority of a followup message. This is a best practice and helps to ensure your messages don't end up in a SPAM folder. However, a video or photo is a great way to add a personal touch to a followup. People respond to visuals in a different way than text, so this allows you to communicate on more than one level. 

An introduction photo or video is a good option for followup sent to new contacts. 

You could also include photo or video when you have a specific property, new offering, or seasonal message you want to share with contacts. 

Of course, these are just general guidelines. Feel free to make your followups authentic and true to who you are. Photos and video make doing this fun and easy.