digiKam is a free, open source application that belongs to the KDE desktop environment and with which you can organize, edit and view your photo collection.
One noteworthy function allows you to preview the photos directly from your digital camera, as well as download or delete them as needed.
Another feature that deserves mentioning is its complete graphic editor, with which you can perform a good number of operations on the images. It includes a number of filters and textures that you can apply to your photos, as well as tools to adjust them in different ways.
All of this makes digiKam stand out among other apps in the same category.