How can I determine whether or not a mobile phone background image is appropriate?

Just for fun, I like to have pretty and interesting pictures on my phone. **Question**: How can I determine whether or not a mobile phone background image is appropriate? As I learned from my earlier question (https://islam.stackexchange.com/q/33642/17163) , tasweer, or picture making, is considered haram, but to what extent is still unclear to me. It's listed as a major sin by Imam Shamsu ed-Deen Dhahabi (48-th on the list of 70 major sins). However, my Muslim friends don't seem to care about this (and, like with statues, it's not hard to find images in Muslim-majority cities; e.g. put [city name] billboard into Google Images ). There seems to be a lot of nuance to this: (a) whether or not one should care at all; (b) making pictures vs. merely viewing the pictures; (c) whether the images might be viewed as promoting haram acts; (d) the images being electronic (cf. https://islam.stackexchange.com/q/1235/17163) . Here are some examples (which I randomly downloaded from the Internet at some point): - A drawing of a silhouette of a woman decorated in flowers: - A drawing of Jack Frost (from Rise of the Guardians ) and Elsa (from Frozen ) sharing a tender moment: - A drawing of a punky-looking, tattooed Asian woman: (I also have unproblematic images, e.g., photos of flowers.) I'm not after an answer limited to these images alone, but a general method for determining if an image is appropriate.