Is it possible to add images to blog excerpts?

I'm currently using the (portfolio) Momentum theme, and would like to incorporate images into blog excepts. Can this feature be introduced, or somehow coded in?
Alternatively, can a 'read more' function be introduced/coded in to hide the remaining post after a specific point? This could allow images in the post to be included in the 'excerpt'.
I only ask as some of my posts can be long, and I like to use an image to introduce each entry. It can therefore be quite a lot to scroll through when a reader wants to see an older post.
Thank you!