With these packages and environment configuration, Chinese and Bangladeshi (and all other languages I've tested) works everywhere: Iceweasel, Opera and GNOME.
$ dpkg -l | grep font | grep ^ii
ii console-setup 1.55 console font and keymap setup program
ii console-terminus 4.30-2 Fixed-width fonts for fast reading on the Linux console
ii defoma 0.11.11 Debian Font Manager -- automatic font configuration framework
ii emacs-intl-fonts 1.2.1-8 Fonts to allow multi-lingual PostScript printing from Emacs
ii fontconfig 2.8.0-2.1 generic font configuration library - support binaries
ii fontconfig-config 2.8.0-2.1 generic font configuration library - configuration
ii gsfonts 1:8.11+urwcyr1.0.7~pre44-4.2 Fonts for the Ghostscript interpreter(s)
ii gsfonts-x11 0.21 Make Ghostscript fonts available to X11
ii gucharmap 1:2.30.2-1 Unicode character picker and font browser
ii kbd 1.15.2-1 Linux console font and keytable utilities
ii libfont-afm-perl 1.20-1 Font::AFM - Interface to Adobe Font Metrics files
ii libfont-freetype-perl 0.03-1 Read font files and render glyphs from Perl using FreeType2
ii libfontconfig1 2.8.0-2.1 generic font configuration library - runtime
ii libfontconfig1-dev 2.8.0-2.1 generic font configuration library - development
ii libfontenc1 1:1.0.5-2 X11 font encoding library
ii libfreetype6 2.4.2-1 FreeType 2 font engine, shared library files
ii libfreetype6-dev 2.4.2-1 FreeType 2 font engine, development files
ii libfs6 2:1.0.2-1 X11 Font Services library
ii libgraphite3 1:2.3.1-0.2 SILGraphite - a "smart font" rendering engine
ii libotf0 0.9.11-1 A Library for handling OpenType Font - runtime
ii libt1-5 5.1.2-3 Type 1 font rasterizer library - runtime
ii libxfont1 1:1.4.1-2 X11 font rasterisation library
ii libxft-dev 2.1.14-2 FreeType-based font drawing library for X (development files)
ii libxft2 2.1.14-2 FreeType-based font drawing library for X
ii ttf-arphic-bkai00mp 2.10-8 "AR PL KaitiM Big5" Chinese TrueType font by Arphic Technology
ii ttf-arphic-bsmi00lp 2.10-8 "AR PL Mingti2L Big5" Chinese TrueType font by Arphic Technology
ii ttf-arphic-gbsn00lp 2.11-9 "AR PL SungtiL GB" Chinese TrueType font by Arphic Technology
ii ttf-arphic-gkai00mp 2.11-8 "AR PL KaitiM GB" Chinese TrueType font by Arphic Technology
ii ttf-arphic-ukai 0.2.20080216.1-1 "AR PL UKai" Chinese Unicode TrueType font collection Kaiti styl
ii ttf-arphic-uming 0.2.20080216.1-3 "AR PL UMing" Chinese Unicode TrueType font collection Mingti st
ii ttf-dejavu-core 2.31-1 Vera font family derivate with additional characters
ii ttf-dejavu-extra 2.31-1 Vera font family derivate with additional characters
ii ttf-freefont 20090104-7 Freefont Serif, Sans and Mono Truetype fonts
ii ttf-liberation 1.05.2.20091019-4 Fonts with the same metrics as Times, Arial and Courier
ii ttf-lyx 1.6.7-1 TrueType versions of some TeX fonts
ii ttf-opensymbol 1:3.2.1-6 OpenSymbol TrueType font
ii ttf-sil-gentium 20081126:1.02-11 extended Unicode Latin font ("a typeface for the nations")
ii ttf-sil-gentium-basic 1.1-2 smart Unicode font families (Basic and Book Basic) based on Gent
ii ttf-sil-nuosusil 2.1.1-2 Unicode font for Yi (a script used in southwestern China)
ii ttf-wqy-microhei 0.2.0-beta-1 A droid derived Sans-Seri style CJK font
ii ttf-wqy-zenhei
Furthermore, I've got these settings:
$ dpkg -l *xfs* | grep ^ii
ii x11-xfs-utils 7.4+1 X font server utilities
$ locale -a
C
en_GB.utf8
POSIX
$ echo $LC_ALL
en_GB.utf8
$ echo $LANG
en_GB.utf8
