This may be a planned capability of Nautilus, but I didn't see any bugs on
it so I will add this bug and let my opinion be known.  I would like to see
the following: the ability to easily create custom filtered views based on
inclusion/exclusion of regular expressions (and possibly several other
options), with the ability to name and save these for reuse in other
directories via the "View as" pulldown menu.  

My suggestion for the most primitive implementation of a "custom" view
would be thus: have a "Custom View" sidebar panel that allows creation of
temporary custom views. Using this panel, one could create a temporary
custom view by filling in two input boxes: "INCLUDE" and "EXCLUDE" with
things like "*.png; *.jpg".  Two button, "REFRESH" and "SAVE CUSTOM VIEW",
would allow the user to activate the current temporary custom view or save
the current settings. When a user types a pattern into the include or
exclude box and presses "Refresh", only the files that match (or don't
match) these patterns will be shown in the view window.  When "SAVE CUSTOM
VIEW" is selected, a dialog prompts the user to give a name to your current
custom view.  The preferences get saved as an xml file somewhere like
"~/.gnome/Nautilus/Custom-View", and all custom views saved in this
directory appears in the "View As..." pulldown list.  The most primitive
implementation would save only the inclusion/exclusion lists and the
standard directory view (icons/list/music) that is currently active.  So,
it enables temporary as-you-need-it filtering, and custom view creation.
When a custom view is chosen from the "View as..." pulldown, the saved
settings get filled in on the panel and the appropriate view gets produced.

This would allow one to create custom views like "NORMAL LIST", which
doesn't show any .*, ~*, or #*# files in the list view, as well as a
"DETAILED LIST" which shows everything.  Or, a "BACKUPS" view, which shows
all .tar.gz, .tgz, .gz, ~*, .zip, and #*#, but nothing else.  Some other
useful custom views: "PLAYLISTS" (only .m3u), "PICTURES" (only show
graphics files in the Icon view), and "DOCUMENTS" (which will filter out
all of the extraneous .log, .dvi, .ttt, etc. files used by LaTeX). One
tricky part of this is to have a clear way telling the user he/she might
not be seeing everything that exists in the directory.

A more advanced version of custom views would allow setting and saving of
other viewing preferences that are currently only available for global
change or are folder-by-folder options; like the default zoom level and the
information to show about each file (size, name, emblem, path, date, etc.)
 A super-advanced version would allow filtering based on mime-type, emblem,
date, and filesize, and have an inclusion/exclusion list similar to
Evolution filters that allowed for AND or OR matching (although I find this
a little confusing at times.)  Another possibility includes a recursive
option which will produce this view for a directory and all its children
(ignoring symlinks).  I'll await the implementation of the primitive custom
view before I file bugs for these more advanced features :-).