Do you need your modal to only come up once per user? this is the tutorial you are looking for from Pixel Geek.
Sort and Filter content on Webflow with MixitUp3. MixItUp 3 is a dependency-free library for animated filtering and sorting. Great for managing any categorized or ordered content like portfolios, galleries, and blogs. It can be used both with static and dynamic content. I have provided the link below of a very detailed page explaining how to make this work. Tutorial created by Anna Sabatini.
If you need your site to generate a random quote or item using Webflow's CMS here is a nice tutorial from Ben Parker on how to accomplish this.
Counter-Up is a lightweight jQuery plugin that counts up to a targeted number when the number becomes visible.
Create a website were you add weekly build challenges. Screenshots, videos, and interactions of website examples are posted. Anybody can join in on the challenge and try and finish it within a week. This would be a fun little side project and people would love a challenge for the learning experience and the difficulty it can bring. Webflow’s CMS will be very useful when constantly adding the challenges. Add the challenges manually with the CMS, let people submit the link of their websites through a form and announce the winners every week! You can automate the form entries with zapier, after every form submitted zapier can create a new CMS item. Go ahead and have fun with this idea!