Add xdg-open as the first choice whenever this seems to be usefull.
Index: lyx/lib/configure.py
===================================================================
--- lyx.orig/lib/configure.py	2013-05-26 23:29:26.833885599 +0200
+++ lyx/lib/configure.py	2013-05-26 23:29:26.829885599 +0200
@@ -547,7 +547,7 @@
     checkViewerEditor('a SVG viewer and editor', ['inkscape'],
         rc_entry = [r'\Format svg        svg     SVG                    "" "%%" "%%"	"vector"'])
     #
-    path, iv = checkViewerNoRC('a raster image viewer', ['xv', 'kview', 'gimp-remote', 'gimp'],
+    path, iv = checkViewerNoRC('a raster image viewer', ['xdg-open', 'xv', 'kview', 'gimp-remote', 'gimp'],
         rc_entry = [r'''\Format bmp        bmp     BMP                    "" "%s"	"%s"	""
 \Format gif        gif     GIF                    "" "%s"	"%s"	""
 \Format jpg        jpg     JPEG                   "" "%s"	"%s"	""
@@ -630,11 +630,11 @@
     #
     #checkProg('a Postscript interpreter', ['gs'],
     #  rc_entry = [ r'\ps_command "%%"' ])
-    checkViewer('a Postscript previewer', ['kghostview', 'okular', 'evince', 'gv', 'ghostview -swap'],
+    checkViewer('a Postscript previewer', ['xdg-open', 'kghostview', 'okular', 'evince', 'gv', 'ghostview -swap'],
         rc_entry = [r'''\Format eps        eps     EPS                    "" "%%"	""	"vector"
 \Format ps         ps      Postscript             t  "%%"	""	"document,vector,menu=export"'''])
     # for xdg-open issues look here: http://www.mail-archive.com/lyx-devel@lists.lyx.org/msg151818.html
-    checkViewer('a PDF previewer', ['pdfview', 'kpdf', 'okular', 'evince', 'kghostview', 'xpdf', 'acrobat', 'acroread', \
+    checkViewer('a PDF previewer', ['xdg-open', 'pdfview', 'kpdf', 'okular', 'evince', 'kghostview', 'xpdf', 'acrobat', 'acroread', \
 		    'gv', 'ghostview'],
         rc_entry = [r'''\Format pdf        pdf    "PDF (ps2pdf)"          P  "%%"	""	"document,vector,menu=export"
 \Format pdf2       pdf    "PDF (pdflatex)"        F  "%%"	""	"document,vector,menu=export"
@@ -642,24 +642,24 @@
 \Format pdf4       pdf    "PDF (XeTeX)"           X  "%%"	""	"document,vector,menu=export"
 \Format pdf5       pdf    "PDF (LuaTeX)"          u  "%%"	""	"document,vector,menu=export"'''])
     #
-    checkViewer('a DVI previewer', ['xdvi', 'kdvi', 'okular', 'yap', 'dviout -Set=!m'],
+    checkViewer('a DVI previewer', ['xdg-open', 'xdvi', 'kdvi', 'okular', 'yap', 'dviout -Set=!m'],
         rc_entry = [r'''\Format dvi        dvi     DVI                    D  "%%"	""	"document,vector,menu=export"
 \Format dvi3       dvi     "DVI (LuaTeX)"          V  "%%"	""	"document,vector,menu=export"'''])
     if dtl_tools:
         # Windows only: DraftDVI
         addToRC(r'\Format dvi2       dvi     DraftDVI               ""	""	""	"vector"')
     #
-    checkViewer('an HTML previewer', ['firefox', 'mozilla file://$$p$$i', 'netscape'],
+    checkViewer('an HTML previewer', ['xdg-open', 'firefox', 'mozilla file://$$p$$i', 'netscape'],
         rc_entry = [r'\Format html       html    HTML                   H  "%%"	""	"document,menu=export"'])
     #
     checkViewerEditor('Noteedit', ['noteedit'],
         rc_entry = [r'\Format noteedit   not     Noteedit               "" "%%"	"%%"	"vector"'])
     #
-    checkViewerEditor('an OpenDocument/OpenOffice viewer', ['libreoffice', 'lwriter', 'lowriter', 'oowriter', 'swriter', 'abiword'],
+    checkViewerEditor('an OpenDocument/OpenOffice viewer', ['xdg-open', 'libreoffice', 'lwriter', 'lowriter', 'oowriter', 'swriter', 'abiword'],
         rc_entry = [r'''\Format odt        odt     OpenDocument           "" "%%"	"%%"	"document,vector,menu=export"
 \Format sxw        sxw    "OpenOffice.Org (sxw)"  "" ""	""	"document,vector"'''])
     #
-    checkViewerEditor('a Rich Text and Word viewer', ['libreoffice', 'lwriter', 'lowriter', 'oowriter', 'swriter', 'abiword'],
+    checkViewerEditor('a Rich Text and Word viewer', ['xdg-open', 'libreoffice', 'lwriter', 'lowriter', 'oowriter', 'swriter', 'abiword'],
         rc_entry = [r'''\Format rtf        rtf    "Rich Text Format"      "" "%%"	"%%"	"document,vector,menu=export"
 \Format word       doc    "MS Word"               W  "%%"	"%%"	"document,vector,menu=export"'''])
     #
