FIG. 1 is a perspective view of my new swan plasma lamp design shown in a position of use with a base; FIG. 2 is a front elevational view thereof; FIG. 3 is a left side view thereof; FIG. 4 is a right side view thereof; FIG. 5 is a front elevational view thereof, shown with an attachment to a base; FIG. 6 is a top elevational view thereof; and, FIG. 7 is a bottom elevational view thereof. The broken lines showing a base or an attachment in FIGS. 1-7 are for illustrative purposes only and form no part of the claimed design.