GBIF provides free and open access to biodiversity data
Some of the aggregated data sources contain images of specimens that with the an open license can be reused.
Tarsier queries the GBIF api for images with CC0 and CC-BY licenses.
Type the scientific name in the form in top right corner and press Submit
If the applicable license is compatible with Wikimedia Commons, it is possible to upload the selected images to commons directly. This requires a Wikimedia account.