1. If you type
{{:namespace:image.jpg?linkonly|Text for the link.}}
only the link to the image is shown, but not the image itself, as you desired.
2. It is possible to save pages and media files directly into DokuWikis data-directory. But you should take care about a few restrictations:
Filenames must not have uppercase chars, whitespaces or other special chars like german umlauts.
Be aware that it can take some time until the external added pages are indexed by the search function if you add a big amount of new pages. The searchindex-plugin can help in this situation.