About this plugin
First of all, this plugin is for a WordPress Multisite setup. The user has the option to display thumbnails or not, and for how many posts they want to display.
This widget works differently than other widgets that display recent posts from an entire network. A network that has lots of blogs (like several hundred, or even several thousand) can take a long time to query each blog and compare the times for the most recent posts.
If you are using some sort of database sharding it will take even more time. This plugin works much more simply, as posts are published on the network they are pushed to a network option that contains an array of the most recent posts from the network.
At first this array will be empty, so it might be a bit until the widget has a full list (up to the maximum set by the user in the widget) of recent posts. Since we are adding posts to the list at the time of publishing this also makes it easy to push the thumbnail to it also, which is why this widget can show thumbnails when lots of other ones can’t.
In a future version we will allow the network admin to limit the people who can use this widget to super admin users. A future option will also allow network options for blogs to ignore (at a network level), blog owners will be able to opt out of having their blog’s posts included, or the network admin will be able to explicitly list blogs that get included.