I couldn't find this suggestion yet, so here it goes.
Would you also like it if there was an ability to send images in/attached to a scheduled message?
A personal use case would be that after booking I like to send guests not just an intro message but also a pamphlet about the Low Emission Zone rules of the city (if they arrive by personal vehicle), and what they can do beforehand to register and avoid hassle/a fine on arrival. Currently there is no way of combining these messages.
This is also tied to the automated display of check in instructions (at what time can guests actually see this, upon booking confirmation? x time before arrival?) where you can actually submit images to make things clearer, but there is no such option for directions or the house manual section.