The text bubbles are supper easy to add through photoshop. I take my png saved renders to photoshop to repair clothing tears etc and add the text bubbles and story lines and then add the site logo/URL..

Text bubbles are created with layers.. one for the bubble, another for the triangle pointing to the speaker using first the oval lasso and then the polygon lasso. These are filled in with white colour with the paint bucket..

Your first layer is your image, then you create your layers for text.. Go back and create two new layers just above the image layer, below the text layer. Say you have just the one text bubble, you'll end up with a total of 4 layers (base image, bubble, triangle and text. Once you have the layers, you make the base and text layers invisable, and merge the bubble and triangle layers (merge visable layers). Then add a stroke to the merged layer, "inside, 2 pixels" for example and then make the base and text layers visable again.. flatten the layers (merging them all) and save as image format of your choice.. 

If you would like more detailed information, drop me a line and I can walk you through it.. simple enough to do.. once you figure it out. 

Cheers