SEO Help for Image Selling site

Site URL: https://birthdaystar.org

I am running an image sharing site, We want to sell our birthday images.

But as much I know about SEO it all depends upon written content. If  I am sharing images in a post then there will be less than 300 words in post.

So in that case how can I do SEO of my site because google may ban me due to less content.
Also please suggest some SEO backlink Source for my images sharing site.

Please Help me....

Google won't ban your site - it simply won't rank the pages with thin content.