You should contact the Maryland Motor Vehicle Administration (MVA) about your specific situation and if your license plates need to be turned in because of your vehicle registration being suspended. The MVA can tell you for certain what in your specific situation is required of you regarding your registration and license plate tags.
In general we can tell you that when your registration and license plates are under suspension you are required to turn them in so that your suspension will officially start. For instance if you have a 30 day suspension you will want to turn in the plates so that they are off your vehicle for 30 days and the suspension will be lifted. If you fail to turn them in then although the suspension may be in place, the state may not count the time towards the 30 day suspension until you actually turn in the plates.
Typically in Maryland if your vehicle's registration is suspended, you must immediately return the license plates to an MVA branch office. If you do not return the license plates within 10 days after the date on which the suspension notice was mailed, a tag pick up order will be issued. The license plates then will be subject to immediate confiscation by a Maryland police officer. So you may your license plates confiscated by a tag recovery agent or the police once the registration suspension is in effect if you have not turned them in yourself.
One reason to lose your license plates and vehicle registration privileges is if you are found driving without insurance in Maryland. To make sure your vehicle is properly covered you can come to an auto insurance specialist such as CarInsurance.com.