In modern online platforms, advertisement plays a crucial role in subsidizing their operational costs. With the emerging advances in generative AI, this position piece explores the potential of running online advertisement systems for Large Language Models (LLMs). Our position is that, the existing framework for modern search advertisement system does not carry over to LLM advertisement. To understand how one could run advertisement systems for LLMs by integrating ads into their outputs and facilitate future research in this area, we introduce a generic framework for LLM advertisement. We explore several aspects of design choices within our framework and propose potential research questions to operate a practical system.