Ideally the icon should have a uniqe touch not yet present in the competition https://play.google.com/store/search?q=expense
and should appeal to an international audience. My Expenses' quality most frequently acclaimed by its users is its concise presentation of transaction lists, the feature image could make reference to this quality (see screenshots). It should be easy to derive a variant from the icon that can be used for the paid contrib app https://play.google.com/store/apps/…es.contrib that unlocks premium features.
File size for Promotional image
1024x500 (24bit png - no alpha)
180x120 (24bit png - no alpha)