Stumble it button code for blogger blog give by StumbleUpon site is not updated for new blogger blog. They have the code for old blogger. The code for new blogger would change to

< a expr:href=’”http://www.stumbleupon.com/submit?url=” + data:post.url + “&title=” + data:post.title’ title=’Stumble It’>Stumble It.</a >

You can get the standard button images here