I use a simple solution
instead of using the Gmail app I use the Google browser on my Android phone and when you send emails from there your signature including the picture comes up just the same way as sending it from your desktop let me know if it works for you

I don't know where you read that turning off the mobile signature would introduce the desktop definition, but it's not true. The app does not have access to the signature defined in the web interface. You must set a separate signature in the app if you want one.

I found that if you have a Samsung Galaxy phone, that the default email app on Galaxy allows for mobile signatures to mirror the desktop signature with hyperlinks. That is the only work-around I've found. The Gmail app on Android, nor iPhone allows for hyperlinks. Google needs to fix this app.

There is no provision for using the web app signature in the Android Gmail app yet. To set a mobile signature, go to Settings > {email address} and scroll down to General > Mobile signature.

Try Nine email this will allow for graphics in your signature, just copy and paste it's that easy

I had been trying to figure this out. If you have the signature in your gmail on the computer you have to go to the mobile app settings and turn OFF mobile signature then your computer signature will show up from the mobile gmail account. You won't see it when you are composing the email but the receiver will see it. It worked for me. Hope someone benefits from this. Good Luck!! Easy Fix