There appears to be no easy way to change the background color of stream item icons due to there not being a class around the span tag that wraps the icons based on the stream type. Right now stream icons use the classes "stream-icon pull-right ml-5".
When attempting to change the background, it does this for all of the stream icons which end up making all of the icons feel the same. So what I recommend is adding classes to the span tags based on their activity type. So for example for an article it could have the classes "stream-icon pull-right ml-5 es-article" which would not harm the display and allow us to change the styling. This would also allow for the icons to natively be styled through CSS instead of inline.
When attempting to change the background, it does this for all of the stream icons which end up making all of the icons feel the same. So what I recommend is adding classes to the span tags based on their activity type. So for example for an article it could have the classes "stream-icon pull-right ml-5 es-article" which would not harm the display and allow us to change the styling. This would also allow for the icons to natively be styled through CSS instead of inline.