I just got my own Picco Neemo and started searching through the tiny clothes I have for what fits.
Mattel Kelly or Chelsea:
Dresses fit as shirts.
Skirts are way too short.
Pants and Shorts fall off as they are too large in the waist.
Shoes won't fit a Picco D.
Fancy Nancy:
Dresses fit as shirts.
Pants, Skirts, and shorts fall off.
Shoes won't fit a Picco D.
Puki Puki
Any thing that fits a Puki Puki as a dress will fit her as a shirt.
Heather and Einin by
faydreams, on Flickr
My Puki Puki is wearing a dress I made for my Picco Neemo. It was too short on Picco but fits the Puki or Kelly dolls just right.
Shoes won't fit a Picco D.
Bratz Kidz:
Pants for Bratz Kidz fit my Picco Perfectly. Right length, and right waist. I have two pair, jeans and a jogging suit. Both fit and allow her to set.
Shirts fit but are a belly bearing short.
skirts fit if they are the long ones. Short shirts look too short.
Shorts I don't have any off so couldn't say, but figure they will be like the pants.
No go on shoes though.
Hope this helps.