Picasa was discontinued by Google, but don't worry we have compiled a list of Picasa Alternatives:
FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
digiKam is an advanced digital photo management application for linux/KDE, which makes importing and organizing digital photos a “snap”. The photos are organized in albums which can be sorted chronologically, by folder layout or by custom collections.
Adobe Photoshop Lightroom CC is a commercial photo processor and image organizer.
XnView is a utility for viewing and converting graphic files.
nomacs is a free image viewer for windows, linux, and mac systems, which is licensed under the GNU Public License v3. nomacs is small, fast and able to handle the most common image formats including RAW images. Additionally it is possible to synchronize multiple viewers. A synchronization of viewers running on the same computer or via LAN is possible. It allows to compare images and spot the differences (e.g. schemes of architects to show the progress).
TagSpaces is an offline, open source, document manager with tagging support.
ImageGlass is a simple picture viewer with which you will be able to display your image collection in a very similar way to the one that Windows provides by default, but with some additional functions. This application will allow you to better manage your pictures thanks to the options it includes and the extension it enables to install for adding more functions and widening its possibilities.
Shotwell is an open source photo organizer designed for the GNOME desktop environment.
The best digital asset manager on the market.
Adobe Bridge is a freeware digital asset management software.
gThumb is an image viewer and browser for the GNOME Desktop. Features Image Viewer.
Enter a world of infinite creativity with the comprehensive photo-editing and graphic design power of PaintShop Pro X8. Accelerate your photo editing with enhanced layers, more precise selection tools, faster brushes and extensive productivity-boosting improvements. Bring ideas to life with the most versatile photo-editing software value anywhere.