@Harsh is absolutely right that you can’t dynamically change backgrounds in Power BI. However, like many things in Power BI, with some ingenuity you can develop workarounds to those constraints. This question came up in another thread recently, related to dynamically changing background colors:
In addition, here are two other recent threads about manipulating transparency values with DAX. I think these techniques could be used in combination with screen sized buttons filled with the desired images and showing/hiding them based on DAX logic and synching slicers (along the lines of @Greg’s suggestion):