Do you know what is SEO? Then how about ASO? ASO is abbreviation for App Store Optimization. If SEO is to optimize your website for search engine, ASO doing same thing for your app in app store. If you do ASO, your app will be discovered by more peoples.
That is marketing. Marketing is not my thing, so if you want to know more, kissmetrics explain better.
Great screenshots will drive people to download your app. Before, I use Device Art Generator to make screenshot on Google Play App page. After a while, I notice note in that page :
Note: Do not use graphics created here in your 1024x500 feature image or screenshots for your Google Play app listing.
There is the rule. So, I stop using it and search for other resource. You know 忍者の世界でルールや掟を破る奴はクズ....
Above will looks better if I have better app UI. I love design of Sony Xperia. So, I create a vector graphic for smartphone that inspired by Sony Xperia design. This graphic can and will be use to create screenshot in app store.
You can download sony experia inspired svg file here. License under CC0, public domain. Use it how you like. I love to know how people will use it, if you dont mind please share your story.