There are a few things you can do with Preview and Finder, however the default image from
screen shot in Finder isn't .jpeg; though that is possible to change the default away from .png.
Preview can be used several ways, however from older OS X versions the feature set changed
and sometimes I don't use the newer computer to handle images even for temporary email items
since the effect just isn't there and for very simple things, third-party software shouldn't be needed.
Appears there are fewer quality purposeful applications included in the most recent OS X, so
one has to look into Apps online; and these are subject to change, when they do, so will your
resulting archived images once they go through a transformation process in a newer app.
However, Preview can be used to look at the contents of a folder, edit some aspects of those,
and then you can test to see if the changed or edited features stick, once emailed, etc. This
is where I'd started using ToyViewer, as it did not create propriety file types and did not need
to be launched to see an image processed by it. And the effects of an edit, stayed put.
You can also select everything in a folder, with Preview and show them together in one window.
Saved changes may be moved to another folder, on the desktop, or managed OK between the
Preview application and actions on items, as provided by Finder.
{Even the windowing effects on desktop + finder aren't as good in Mavericks 10.9 as they were
back in 10.5.8. Many items that were tolerable and stable in Snow Leopard, a good system,
have been changed, too. The size of an open window has been restricted, among other items.}
Hopefully you can find a suitable software or a process using fairly good alternatives
to some costly bloatware you may not need, to proceed in your image projects.
Good luck & happy computing! 🙂