Not necessarily. While word count and image count do affect how Google ranks your hubs in search results, the correlation is weak because there are other factors at play, some of which may counteract one another.
You know from your own experience using Google that pages with a few paragraphs can easily out rank a page with much longer content. Why? Many reasons. 1) the page with less content may be older, 2) the page with less content may be on a site that is more trusted e.g. Wikipedia vs content mills like HubPages, 3) the shorter article may be balanced out with more media like pictures and video, 4) the shorter article is written better while the longer article is keyword stuffed with nonsense.
Don't think that just because you've written more than 700 words you're in the clear. And conversely, if you've only written 500 words, don't despair that every longer article is going to out rank you. Consider all the factors.