Hey! I was just writing a collage tutorial for PicMonkey and they just launched their collage abilities!
You MUST go over there right now and try it out. It's very intuitive and there are a ton of different collage styles to try out. You can even create your own personal style! However, there is not a text feature when you are working in the collage section. You will have to save the collage to your desktop and then reload it in PicMonkey's regular photo editing section. Remember you can use all your own design elements in PicMonkey and have either a transparent background or a color of your choice (including white) too.
To stay on top of PicMonkey's updates you may want to follow them on Facebook! Stay tuned for my How To Make a Blog Banner Using PicMonkey next week!