Is there a way to create a "sticky" asset I have a list of images that are loaded directly from the content of a specific asset folder.

{% for image in craft.assets.find({ folderId: 18, limit: 240, order: filename }) %}


What I want to achieve is that one (or more) images from that assets folder are listed first (second etc.) before the actual ordering by filename starts place. 
Much in the same way as sticky entries (EE).
Based on adding a lightswicht ("sticky") as suggested by @carlcs I think you should be able to solve this by just using two order fields.

{% set images = craft.assets.folderId(18).order('sticky desc, filename asc').limit(240); %}


You should be able to save some twig code, maybe even requests. Haven't tested this though.