As far as I know, SVG is an open standard for vector graphics that is supported by browsers and many graphics editors. It is ideal for web graphics and other vector images as it allows you to scale the graphics without losing quality. Also, PDF is a universal document format, but it also supports vector graphics. Vector objects can be embedded in PDF files, making them suitable for printing and sharing. Therefore, only you choose which one to use. But if you still haven't found a place to download such photos, I recommend depositphotos, where I recently searched for many different tardigrada photos.