Photographic assets
JPG and WEBP are often the practical choices for photography-heavy pages. They keep file weight lower than PNG and are easier to scale across large content libraries.
Graphics and transparency
PNG still makes sense when you need dependable transparency and straightforward editing. WEBP can also handle transparency, but not every internal workflow is equally comfortable with it.
Operational recommendation
Pick a default format for web delivery, then use conversion tools or API automation to handle exceptions. That approach usually scales better than asking every contributor to export the perfect format manually every time.