Be warned: the approval process can be slow. However, big brands are available here with a standard commission rate.
Companies with a primarily consumer audience are the biggest market for affiliates, but they're certainly not the only option. Political candidates or other celebrity figures may turn to affiliates for endorsement, as will commercial or private entities that may want to boost their reputation to the public.

A number of them include “hover over” sharing buttons that pop up when someone moves over your photos and gives them the ability to share the pic and link to their own Instagram or Twitter feed so that their friends can access it too.
It is worth thinking about setting up a posting structure or schedule. For your blog writing, you may be comfortable sharing two or three posts a week, or maybe once a month is really all you can commit to.