Irfanview (free) can package your images into a nice single executable slideshow that you can attach to your email.
Just change mysideshow.exe to mysideshow.rename-as-exe before you send it since most email clients are suspicious of executable files.
Or you could just zip the images and send them as a zipfile.
Mac
PS: Here's a little forgotten gem:
Use a Built-In Windows Utility to Create Self-Extracting Archives