Sometimes I create signatures for people who want to upload them to blogger themselves. If you are willing to play with your blogger dashboard - try uploading your signature permanently using the following steps:
Step one - have me create you a signature (LOL!) Just kidding - make sure it is the same background color as your blog or get one with a transparent background (ie. PNG file)
Step two - Create a post and upload your signature as a photo to a post in your COMPOSE tab
Step three - click on the EDIT HTML tab and copy the HTML code of that photo
Step four - DO NOT PUBLISH YOUR POST (you can add a title to the post ~ for example - DO NOT DELETE - BLOG SIGNATURE). Save your post, just do not publish it.
Step five - go to the SETTINGS Tab in your dashboard.
Step six - click on FORMATTING tab and scroll ALL the way to the bottom of the Formatting page. You will see a POST TEMPLATE box.
Step seven - paste your HTML code (from your signature) in the Post Template box.
Step eight - save your settings
Now each time you create a post, your signature will automatically pop up in the compose portion of your post.
Variations: Since I upload so many cards and I was tried of writing "Supplies" - I created a custom Supplies graphic which atomatically uploads each time I post - if I don't want to use the supplies graphic (ie. if I am not posting something with a supply list), I just click on the graphic and delete it!
Hope this helps!