Original model, texture and shirt from this!!
https://www.gtainside.de/en/gta4/skins/195260-v-neck-tee-for-niko-bellic/

I just put a cat on the texture

How to install :
make sure you have OpenIV or SparkIV
Go to :
Grand Theft Auto IV\GTAIV\pc\models\cdimages\playerped.rpf
Drag and drop the file