Is content enough for SEO?

[Jake]

Only authority sites that webmasters willingly link to can get ranking without an aggressive backlinking campaign, be aware that increased quality standards require you to get quality links from relevant sites and mixing up the sources and link types to maintain a natural link profile is important.

Image sites are tougher for the search engines to rank, adding some short paragraph descriptions would really help their spiders categorize your site, at least use descriptive image file names and alt text so they can get some traction in Google image search.