Images aren't the only factor that could cause low page speed score. If you check suggestions from PSI or another speed checker (f.e. GTmetrix), you will find out that there are few things that matter. I mean here the scripts and stylesheets used in your theme. You're using Wordpress so install some optimization plugins like Autoptimize or WP Super Cache. It allows to reduce scripts size and enables the caching system.
Yes, @onebacklinkman is absolutely right images are just one factor that affects your page speed. Apart from images, there are several other factors that contribute to low page speed:
This is the direct cause when a user pings your website through their browser. If the hosting service you are using for your site is not working well for you it lowers down your page speed.
Also, the server location can be a cause for your low page speed. Farther the server from the server, longer the site will take to load.
Too Many Redirects
Redirects are inevitable but too many redirects can lower your page performance. Try eliminating those pages from your that are of no use or return error 404.
Too Many Plugins
Plugins help you extend the core features of the website design platform, but adding too many of them can bring a negative effect to your page speed. Remove the plugins that are not bringing any measurable benefit to your site.