url path for email signature logo

We have moved to Squarespace from an older website format. Previously we used a url link to the old website to provide the logo in our email signatures. In the format of:

http://www.mywebsite.com/themes/mywebsitetheme/images/logo.png

Is it possible to create such a url via Squarespace so that the email signatures will still work?

Edit: I should have written that I hoped to create the same url in Squarespace, so that the signatures in past emails already sent will still work