You can frozen also the sample and try to see them with a SEM. It was posible to frozen samples in the ULTRA FE-SEM of ZEISS, but never tried with liposomes. You can try to take a look about possibilities with this kind of equipment.
Basic TEM will burn them...and even if you stain the sample I woudn´t expect to see much. I know in our center people use to do crio-TEM for liposomes.
We have tried to capture liposomes in TEM. I think it should work for you as well. for SEM, try minimal diluted sample dried in air or under IR. if liposomes, try air drying. this should for you.