You can use retrun file, for returning an Image file:
return File(sel.ImageStream , "image/png");
and on your view you can call your action result
<img style="width:260px" src="@Url.Action("ActionResult", "Controller")" alt="myimage" />
I Hope it help you,
But about your code, didn't you assign viewdata collection in your controller?,it doesn't work if you don't assign any value to it, and also i think it is only for simple data types, and not for blob data.