As I can see,you are at the begining with making of signatures.
I know you try to make them good but please remember a signature must not exceed 200x700 px and 120kb.(as long you'll save it in .jpg format,there will be no problem with the size )
But try to not make simple mistakes..
Always save it in jpg format not png,usually png exceed 120kb.
It seems you make a lot of them 700x250,700x230...worng.
Please resize them and don't make such mistakes in any further sig.