android/app/src/main/res/values/strings.xml and change to your App name.
android/app/build.gradle and change to your name own.
We use image size with 1242 pixels wide and 2436 pixels tall
You can work off of this Sketch template if you like
android/app/src/main/res/drawable/splashscreen.jpg and change to your image.
Don't forget clean cache after change app info.
cd ./android && ./gradlew clean