Ask everyone to bring an item of clean old clothing.  

make teams of 3 to 6 people a team depending on number of people.
One person in each group is the 'store' dummy and strips.  The teams
then dress the volunteer only with the clothes they brought for the party.

An option would be to collect the clothes as people arrive and put them
in a box.  People would then get handed one article of clothing per
person from the box.

Once the volunteer is dressed, everyone votes on who is best dressed,
most interestingly dressed, etc.

another option would be to describe the rules and then ask who wants to
be the clothing dumies.  They then proceed in order to select the members
of their team and once the teams are selected the clothing is handed out.

another option is to blindfold the team members so they have to dress
the volunteer team member by touch.

Another option is instead of bringing clothing, each member of the team
has to donate an article of clothing that they are wearing.