I went and searched through all the system files and heres a list of all the planet types i found, there may be more than this, but these are the ones used in the game,
pardon me if any of these are repeats

The List:

archetype = planet_desert_800
archetype = planet_rckdes_1000
archetype = planet_gasgrncld_3000
archetype = planet_earthgrncld_4000
archetype = planet_ice_blue_2500
archetype = planet_icemoon_2000
archetype = planet_earth_3000
archetype = planet_ice_200
archetype = planet_gasblucld_3000
archetype = planet_icemoon_1500
archetype = planet_earthcity_3000
archetype = planet_earthgaia_1500
archetype = planet_ice_purple_1500
Archetype = planet_desorcld_800
archetype = planet_watblucld_1500
archetype = planet_gasicecld_2000
archetype = planet_gasblucld_1000
Archetype = planet_desored_2000
archetype = planet_desorgrck_2000
archetype = planet_neutron_800
archetype = planet_desorcld_500
archetype = planet_icemntcld_2000
archetype = planet_rckbrn_2000
archetype = planet_rckmnt_1500
archetype = planet_icemoon_800
archetype = planet_moonred_1500
archetype = planet_gaspurcld_3000
archetype = planet_crater_800
archetype = planet_mercury_800
archetype = planet_desored_1500
archetype = planet_icemoon_800
archetype = planet_ice_blue_2000
archetype = planet_watblucld_2000
archetype = planet_watdrkcld_4000
archetype = planet_gasgrncld_5000
archetype = planet_storm_5000
archetype = planet_gasorgcld_5000
archetype = planet_gaspurcld_5000
archetype = planet_watblusmlcld_2000
archetype = planet_watbluislcld_4000
archetype = planet_moonblu_1000
Archetype = planet_watgrncld_3000
Archetype = planet_icemntcld_2500
Archetype = planet_earthsnwcld_2500
Archetype = planet_moonblu_2000
Archetype = planet_mercury_200
archetype = planet_gasblucld_1000
archetype = planet_desormed_4000
Archetype = planet_icelndwat_3000
Archetype = planet_crater_1000
archetype = planet_icewatind_3000
archetype = planet_gasblucld_3000
archetype = planet_icemoon_2000
archetype = planet_earthgrnice_3000
archetype = planet_moonblu_1000
Archetype = planet_watblucld_3000
Archetype = planet_gasblucld_5000
Archetype = planet_icemntcld_2000
Archetype = planet_desert_600