@jmillan, I know next to nothing about smartphones. The little I do know is they mostly work perfect in bright sun, so that may be the scene you want. As for a background, whatever you prefer of color is up to you. A simple sheet of very large cardboard will do. The link above gives some useful insight, and many of the tips and tricks can be transferred to smartphones. As Eric Berg points out, do NOT use digital zoom - it is always better to edit in one of the many free editing programmes. Should you ever invest in a camera, I have had tremendous use of my Olympus TG4 (now out of production, they launched TG6 now) the price is far below that of an Iphone, and the TG-series is watertight, comes with a editing programme, has a movie camera, and - best of all - the new TG6 has a focus-stacking function that will allow you to make a composite photo that will enable you to have the focus in the right place from tip to tail.
Sorry - it was not about smartphones, but as mentioned above, the best results are with a tripod and timer. Hope this was of some use - happy modeling, and have fun with your pictures too!
