I noticed that no one really did Niko in the GTA V style for GTA IV and decided that it would be worth doing something like that. Nico now has green eyes, thicker hair, and improved clothing.
Changes:
The head texture is taken from the model and the outerwear is taken from the Niko model from GTA V;
The pants and boots are taken from Franklin Clinton from GTA V and repainted in the original colors. I did this because in GTA V the Niko model has no legs.
Installation:
Just move playerped.rpf to GTAIV/pc/models/cdimages with replacement. Just in case, you can make a backup.