Sure. Go to Lunapic. It'll take a bit, but it can be used over and over.
Upload a blank, solid color image. If you don't have one, the blank memes here will work if you select a solid, single color. Black or white works well.
Upload your solid color image. Go to edit, and select transparent. Select the color to make transparent, and now you have a clear canvas to put your text on.
Go to the menu, select draw, and add watermark. White text @ 50% transparency looks best. Type your signature in and finalize it. Next, go to edit And select autocrop. That trims away the excess, which makes it easier to put where you need it. save as a png file.
The key on using a watermark is to keep it out of the way. Notice my usage above, in my original comment meme. Out of the way, non distracting, but easily seen.