As stated here, there are a number of different creatures mentioned in scriptures, one of them being the Vinayakas. As per the answer, they are described as:
Vinâyâka(विनायक): Malefic spirits ruled by Ganesha that cause all sorts of obstructions.
It is pertinent to note the description of them being those that cause obstructions and being under Ganapati, the remover of obstacles.
The Puranas often group them alongwith other Shiva Ganas like the Bhuta Preta:
रुद्रस्य पार्षदाश्चान्ये घोरा: प्रेतविनायका: - The parshadas of Rudra, the scary Pretas and Vinayakas.
This matches with the above link to Ganapati, being the leader of Shiva ganas, the Vinayakas being among them.
I would like a description of these creatures like this, the way they look (humanoid, combination of human and animal, deformed etc), what they eat (flesh blood sweets, etc), what they do (what sort of obstacles they cause) and other such details from scriptures, especially tantras and/or Puranas.