It would be great if we could lock write access to Assets the same as can be done for pages. We have a situation where our online catalog is built using a large number of assets so that other editors can use that content on their own pages. However, these editors also have the ability to edit those assets which is starting to create problems.
You can lock assets by folder, just as you can for Pages. A few Asset folders cannot be modified (uploads and forms) but all the folders you create in the Asset library have the same folder security settings as site sections and site folders.
If someone tries to click to edit an asset from a page, the asset’s folder is checked first. So even if a user has write permission to a page they may not have permission to edit all the assets on that page due to the asset folder permission settings.
Post again if this doesn’t solve your need.