It's a small part of SEO granted, but still important to remember that page size can be a factor in organic search engine results.
Whatever phrase you are looking to optimize, just look at the top 10 on Google and you will see the page sizes are mostly under 50kb. This is a size that I would recommend being the maximum for most landing pages.
The best way to achieve this is to have smaller pictures and a less complicated navigation, but there are many other ways to keep it down. Call if you want a quote on an SEO package to discuss how to get to the top of the search results.