Yes, it is in settings.

Open settings, tap on the email account under Accounts, then Sending mail, then Manage identities, then Initial identity.

Signature is at the bottom.

is it possible to make HTML or image signature*

It depends on the email app you're using. Gmail, Outlook, and some other apps allow you to set a mobile signature, but they often don't support rich formatting like the desktop versions. Check your app’s settings under "Signature" to see available options! Android's email apps have limited support for HTML signatures. Some email clients allow basic formatting, but for a full Android email HTML signature, you might need a third-party app or manually insert the HTML code if supported. Have you tried any workarounds?"