Most Likely undertaker
you right click on the image and click set as backround
image gallery
Clip Organizer
an area in Photoshop were all the image files appear simultaneously
See Related Links for a Google image gallery of Invertebrates
A long press of an image will give you the options box. Pick "Save image" and it will save into the Nexus 7's Gallery.
image flowers
Hold your finger on the image, and choose Save Image. It will then be loaded into your photo gallery. From there, any app can access it.
jessica-lynn-valerio (this name appears in one of the image tags)
If you come across an image you like, simply long press that image, and a pop up will appear. Look for "Save image", and it will go to your Download folder. You can then go to your Gallery app, and the image should be saved in there.
Try NASA's image gallery page (link below).
IrfanView (search Google) will open most kinds of image file, even if they have the wrong extension.