Here is a list of all the flags I've done and plan to do.
List of core flags to do:
[x] Imperium of Man
[x] Space Marine Legions
[x] The Inquisition
[x] Adepta Sororitas/Sisters of Battle
[x] Grey Knights Chapter
[x] Deathwatch
[x] Imperial Guard/Astra Militarum
[x] Legio/Adeptus Custodes
[x] Adeptus Mechanicus
[x] Dark Mechanicus
[x] Chaos Space Marine Legions

List of Warhammer requests after:
[x] Tau Empire
[x] Black Templars Chapter
[x] Crimson Fists Chapter
[x] Blood Ravens Chapter [ ] Alternate
[x] Astral Knights Chapter
[x] Carcharodons Chapter
[x] Lamenters Chapter
[ ] Angry Marines Chapter
[ ] Minotaurs Chapter
[ ] Sons of Malice Chapter
[ ] Mantis Warriors Chapter
[ ] Adepta Sororitas Orders Militant
[ ] Death Korps of Krieg Regiment
[ ] Elysian Drop Troopers Regiment
[ ] Tanith First-and-Only Regiment
[ ] Tyranids

List of non-Warhammer requests after that:
[x] Zeon Forces (Gundam)
[ ] Earth Federation (Gundam)
[ ] AEUG (Gundam)
[ ] Helghan Empire (Killzone)
[ ] Rachnera {Monster Musume)