You just need to make a small change:
var items = from item in rssFeed.
Elements("response").Elements("results").Elements("game")
select new
{
Image1 = (string)item.Element("image").Element("medium_url")
};
or
var items = from item in rssFeed.
Elements("response").Elements("results").Elements("game")
select new
{
Image1 = item.Element("image").Element("medium_url").Value
};