It would be great to be able to insert tables into editor especially for logos next to text. Other possibility would be to be able to tweak the HTML code of the signature.
In the latest version of Ancoris Signatures, there are now options to created tables directly in the editor without the use of HTML:
See the following article for guidance on editing signature templates: Creating/Editing a Signature Template
Just a clarification, it is possible to tweak the HTML code via the HTML editor by clicking as shown below. You can toggle between the WYSIWYG and HTML editor this way.