https://commons.wikimedia.org/

Wikimedia Commons is a media file repository making available public domain and freely-licensed educational media content (images, sound, and video clips) to everyone. The basic rules of Wikimedia Commons are centered around copyright status, educational purpose, and formatting. Here's a simplified overview:

Free Content: All content uploaded to Wikimedia Commons must be free for commercial use and modification. This means the media must either be in the public domain or released under a free license that allows anyone to use it for any purpose, including commercial and derivative works, as long as they follow the terms of the license (such as attribution).

Educational Purpose: The content must be potentially useful for educational purposes. This includes images, sounds, videos, and other media that can be used for teaching, informational, or scholarly purposes.

File Formats: Wikimedia Commons accepts a variety of file formats, but they prefer formats that are open and can be used and edited with free software. Common formats include JPEG for photographic images, SVG for drawings and maps, OGG for sound, and WebM for video.

No Copyright Violation: Users must only upload content they have the legal right to distribute. This means either the content is their own work, or they have permission from the copyright holder to release it under a free license, or the content is already in the public domain.

Proper Licensing and Attribution: Uploaders must provide clear information about the copyright status of the content and the license it is released under. If the content is not their own work, they must also provide information about the original source and the author, as well as proof that it is legally allowed to be uploaded to Commons.

Quality and Usefulness: While Wikimedia Commons is not strictly about high-quality content only, extremely low-quality content that is unlikely to be of educational or informational use may be deleted. Also, duplicate files and very similar files where a better version exists are usually not kept.

No Personal Photos: Commons is not a personal web space or social networking space. Personal photos that are unlikely to be used for educational purposes may be deleted.

Respect for Privacy and Personality Rights: Even if a photograph is freely licensed or in the public domain, subjects in the photograph may have privacy or personality rights that limit its use, especially for commercial purposes without their consent.

No Offensive Content: Content that is purely intended to shock or offend, without any educational or informational value, is not allowed.

Here is an Image Search for "Tulips"