maybe go down to spot ligiht and purchase a floor rug of your colour and pattern choice and put it on top of the other, old carpet.
stick to old fashioned colours; red, brown,black, cream, bottle green...

Boy, that is one ugly rug. Can you talk to the landlord and go halves on replacing it? Looks like a small area so you might be able to get a remnant in a neutral tone for not a lot of money.

Maybe? if you used a large hemp rug, then you could always bring with you when you move, as it's an easy rug to decorate with. Then add a smaller hemp rug in the kitchen to tie the rooms together. I think they will suit the brick and wood and would work with your modern furniture. Or as mentioned above, maybe you/landlord could split on th costs of a remnant. Good luck.