I’ve mentioned this a couple of times in the past but I agree with the use of optical codes (including QR codes, snapcodes, those circular Facebook messenger codes, etc).
My considerations for codes are the following:
The purpose must be obvious
In your case, I don’t think the generic in the middle is giving enough context. A basic black and white small code would probably work just fine printed providing that there is context around the code to explain what it is. On screen I’d try and use the graphical golden ticket on the same screen if not on the code itself.
Best example of this I’ve seen is Xbox One download redemption codes where it’s printed double sided, code on one side and the artwork on the other such that you’re looking at the item you’re redeeming in when you hold it up (has the side effect of being able to take pictures of the item without exposing the code).
Here’s an example of a few fronts.
And some backs.
The target app must have a built in reader
iOS doesn’t have one built in, neither do most flavors of Android really. You don’t want to make people download an additional app just to scan your code that may be of questionable value to them, takes longer than just manually entering a URL (IMO, this is why QR codes failed in the western world). Snapchat’s codes work so beautifully because when you open the app, the camera is the first thing you are thrown in to and it’s one swipe down to see your own code. In this case, there would need to be a reader in the app on the waiting list to scan a physical golden ticket in.
The code should be as high contrast as possible
Monzo’s branding colours don’t lend themselves well to this sadly. Solid black and white is standard for QR codes for a reason! To add to this, the higher the density, the less readable the code becomes under anything other than ideal conditions.
QR codes should really be a URL with a human readable copy of the data
Solves two problems, one is that it provides a fallback if somebody uses a generic code scanner, it also allows users to do something with the code if they do not have a device with a working camera or are in a low light situation (matters less for codes scanned off screens verses paper).
There are probably other things that I’m forgetting right now but those are the major points.