Hi,
You can try inserting your own HTML signature.
Requirements: Android 5.0 or newer, app settings -> composing and sending -> use new editor turned on (is the default).
This feature lets you use your own "pre-cooked" HTML code in signature settings.
To use this, first switch the account's signature editor window into formatted text mode if not already done so. There is a button / panel for it above the text input area.
Second, just paste your HTML code into the editor. You should see the "content" of your HTML code with formatting, images, and whatever you have there - and not the "raw" HTML code itself.
If it fails and you see "raw" HTML code instead - please be sure that your HTML code (snippet) is well-formed.
We check for a valid HTML opening tag (with or without attributes) at the beginning and a valid HTML closing tag at the end. The two tags need not be the same.
Thanks,
Nadia