Hi asabbioni and welcome to the forum,
I am not aware of the court cases you mention, but given your description, I think they are likely to be ones in the USA - perhaps you have in mind
the case of LeBron James's tattoos in the Take Two game NBA 2K16. Assuming you are based in the UK, cases like that are not really going to assist you. UK law only recognises a
fairly narrow set of exceptions for fair dealing purposes, and these do not include the need for verisimilitude. At best you may be able to get away with having fairly small and indistinct versions of album covers - ones which would be recognisible to hardcore fans, but were not faithful reproductions of the artwork, rather like a very lo-res thumbnail. The 'defence' for doing this would then be, not that it was fair dealing, but instead it was the case that no
substantial part of the original work was copied. However, the only way such a matter could be decided would be in court, which is obviously what you are trying to avoid. To estimate how likely that might be requires you to second guess how the copyright owners are likely to react.
I think the album covers are more likely to be the cause of any complaint, rather the posters for gigs. Posters generally have no intrinsic economic value (except possibly as second-hand collectable memorabilia which is a seperate matter), because they are only issued once and their primary purpose ends once the gig is over. On the other hand albums are sold over long periods, and indeed can be re-issued if a new generation of fans suddenly becomes interested in collecting vinyl. Thererfore the record companies are more likely to want to protect their intellectual property investment and this might include taking action against anyone making reasonable quality reproductions of their album covers, even though you weren't selling the covers.
If you are in doubt about this, it may be worth asking for permission, assuming that there aren't too many separate record companies involved.
There is something ironic about this situation. If you were making a video which was filmed in a real rock music studio and there were album covers on the wall, and these would be visible in the baclground, you could probably rely of the fair dealing exception for incidental inclusion (
section 31 Copyright Designs and Patents Act 1988), but since you are creating the backgrounds graphically, that defence would not apply because you would be making a conscious decision to include the album covers, hence their presence would no longer be 'incidental'.