Working on a new blog design

Perhaps you already saw, that I'm working on my blog. It'll get a complete new design. Unfortunately the signature on my older post had no transparent background... arrrrrrgh. Now it has the cream coloured background and I can't find a way to fix it. So if anybody has a clue how to do that (I know, I could go to every single post and change it - but I'm to lazy for that task...:) ) PLEASE let me know.

...................Hours and hours and hours later......... I think, we have to live with my "background".
But I hope, you like the new design. I'd be happy to know what you think about it.

Have a wonderful day and don't get a brain overload like me