For normal imageset viewers, you can supply the images in a comma-separated list:
asasset=SPSCompanyName/s0427680_sc7,SPSCompanyName/s0414977_sc7
For Mixed Media Sets, the notation is little more complex, as it's necessary to supply the asset type to the viewer.
Here is an example:
SPSCompanyName/s0427680_sc7;;image;,SPSCompanyName/s0414977_sc7;;image;,SPSCompanyName/s0414975_sc7;;image;,SPSCompanyName/s0414973_sc7;;image;,SPSCompanyName/s0414981_sc7;;image;,SPSCompanyName/918297;SPSCompanyName/918297;video;
Putting an example into a URL:
http://domain.scene7.com/skins/Scene7SharedAssets/desktopViewers-AS3/MixedMedia.swf?company=SPSCompanyName&contentRoot=/skins/&videoserverurl=/e2/&vidServerUrl=/e2/&config=Scene7SharedAssets/Mixed_Media&serverUrl=http://domain.scene7.com/is/image/&stageSize=725,630&company=Scene7SharedAssets&asset=CompanyName/6370470_alt;;image;,CompanyName/BADGE%20TEMPLATE?$Product=is{CompanyName/6180570}&$badge=CompanyName/amazingvalue;;image;;
If the template is set as the first item, only it displays.