Here are some links with information and pics:
Oboe d'amore
infos:
http://cc.oulu.fi/~tjamsa/damore.htmlpicture:
http://jdb.psu.edu/music/oboe_am.html
Bass flute
http://www.contrabass.com/pages/flutes.html
Heckelphone
http://www.contrabass.com/pages/heckel.html
Contrabass clarinet
http://www.contrabass.com/pages/cbcl.html
Euphonium
http://users.quista.net/euphbass/euphonium.html
Natural trumpet (you'll have to scroll)
http://www.vsl.co.at/english/instruments/brass/trumpets/trumpet_in_c/History.htm
natural horn (hunting horn)
http://www.vsl.co.at/english/instruments/brass/horns/horn_in_f/History.htm
Aida trumpet:
what distinguishes the aida trumpet from other trumpets is above all the straight tube. Hope I'll find a pic.
cheers,
sabine