I second the recommendation to check out this book. You still have a few days to get in on the Kickstarter, if you want to go that route rather than waiting for the book to be published. It's being done by Kobold Press, so the people involved have worked closely with WOTC in the past and have experience designing monsters for D&D 5E. It should be a nice-looking book, as well.For example: Tome of Beasts