Have you tried loading the image from the database and providing it using a servlet? Does this cause the image to be animated?
If so, please file a jira issue.
I have not done the servlet testing, yet.
In the browser's page information dialog I can see:
Image size when embedded by : 740 bytes
Dynamic image size when embedded by <s:graphicsImage>: 1134 bytes ?!
Original file size and database file size are both 740 bytes.