Older children (4-5 year olds) enjoy playing dress-up with clothes but toddlers normally haven't developed enough dexterity to manage this game. What they can handle is beads, bracelets and hats. Provide a mirror so they can see themselves wearing the accessories. If your tot is still very oral it would be wise to choose beads that have an embedded string (like Mardi Gras bead) rather than strung beads which could become a choking hazard if the string breaks.
Photography Note: You can sometimes get great pictures of tots dressing up by standing behind them and taking a picture of them in the mirror. With the advent of digital cameras toddlers quickly learn that they can see pictures on the back of the camera and it gets harder to photograph them because they stop what they are doing and want to see the LCD display. Photographing them in a mirror makes it a little harder for them to see you especially if you stand off at a bit of an angle.