Hey @Eshaan_Kaul 
That's a great question! We've managed to involve product designers a couple of times in recent memory (on this call and this call). This involved a high level design crit for Collect and also some work on a mock up for a "reskin" and resulted in an effort to move towards Material Design which is currently in progress.
I've been experimenting with a design repo for Collect which you might find interesting. In there I've been working on a Style guide (using the Material Theme Plugin for Sketch), mockups/prototypes for new features and also user research.
In terms of upcoming help you might be able to provide, it would be really useful to pull in a designer on new features to help with mockups or to provide criticism on proposed changes. I'd say joining the Slack and introducing on both #collect-code (our Android app) and #central-code (our newer server) would be a good idea as that would be a good place for people to pull you into conversations. An example would be this discussion around a new user flow we're introducing.
Do you have any experience with conducting user research or writing research scripts? That might be another area you could help out in.