Are you sure you want to put your image based backup into an encrypted container? Remember you need to be able to actually access the data in the event that you need to restore the entire image; decrypting the Veracrypt container first isn't going to be something the normal procedure that restoring a Windows backup image would support (although it's likely technically possible, it may not be straight forward).
Veeam has built in support for its own encryption, although I'm not sure if that is reserved for the full enterprise product or if it's available in the free version.
Edit:- as a potential workaround, if it lets you backup to a network location you could probably point it to your drives administrative share.
So if your encrypted container is mounted to W: then you could access it via the "network" using \\localhost\w$