It is possible to delete the bigip Available Images?
Or it could cause any problem?
Yes, you can delete these. However, when installing hotfixes you'll also need to have the relevant base image available. The hotfix relies on the base image. In your situation I would not delete the 12.1.0 image. You will need this when installing hotfix for 12.1.x.
Note that the newer point releases do not depend on the base images being available.