Hi,
I think you can you use
onerror property, if your image not found the set default image.
like that..
<br />
<img src="data:image/jpg;base64,<%# Eval("img") != System.DBNull.Value ? Convert.ToBase64String((byte[])Eval("img")) : string.Empty %>" />
Maybe it is help full for you.
Thanks
Mohit Saxena