Q. Is it permissible to perform Salaat in a cell where pictures of people are hanging on the wall?
A. If you are able to remove the pictures or cover them up for the duration of Salaat then do so. If you are not allowed to do so or if doing so will develop in an argument or fight with the non-Muslim cellmate, then perform your Salaat even if there are pictures. Since you have no control over such things in prison, you will not be sinful for performing your Salaat in the cell.