Unfortunately there were not many talks about same hypothetical Kings of former Austrian and Russian lands, at least not as in XVIII and XIX centuries. The main cause was that there was little control on this far territory, some violent revolutions made monarchical solutions impracticable and many possible candidates were from Central Powers. But there was something, so here there are some ideas and possibilities for monarchical states in former Russian and Austrian Empires after WWI:
Fredrick Charles of Hesse was briefly elected King of Finland in 1918 but never crowned due German defeat.
Wilhelm of Urach was invited to become King of Lithuania as Mindaugas II in the same period, as proposed by the influential German-Baltic Lithuanian aristocracy.
The Duchy of Curlandia and Semigallia could not be offered to Wilhelm II himself, so the new Duke/King could be Karl, Prince Biron Von Curland, descendant of former Dukes of House of Biron.
The rest of Latvia and Estonia could formed the United Baltic Duchy imagined by Germans to be offered to Adolf of Mecklenburg.
For the Polish Crown there were many candidates (Prince Leopold of Bavaria, Duke Albrecht of Wurttemberg, the House of Wettin of Saxony, that gave two sovereigns to Poland in the past), but Archduke Charles Stephan of Austria, a Austrian-Polish member of Hasburg family, appeared to be the most palatable for Polish.
Charles Stephan's younger son Wilhelm was always a strong supporter of Ukrain nationalism and could become King of Ukraine as Vasyl I.
Hungary wanted to become an independent nation but keeping Charles I of Hasburg as King, and this was avoided only as Western Powers strongly opposed the idea (in fact Hungary officially was a monarchy until 1945, with Admiral Horthy as Regent for Charles I and then his son Othon). An other idea that Horthy considered strongly was to claim the Crown for himself.
If Slavonia (alias Croatia plus Slovenia and Bosnia) doesn't want become part of Yugoslavia it has to follow the Hungarian example: becoming an independent kingdom with Charles I as nominal monarch. Charles approved the creation of Slavonian autonomy state shortly before the fall, in a last attempt to save his Empire. The only alternative, if they don't want be part of Yugoslavia, is to put a Savoia in charge, Emanuele and Victor Emanuel of Savoia-Aosta, Ferdinando of Savoia-Genoa or King Victor Emanuel III himself.
Yugoslavia would be limited to Serbia, Montenegro and Macedonia.
Italy had some ambitions in Montenegro as Victor Emanuel III married Helena of Montemegro but I don't think possible avoid Yugoslavian union with Serbia.
If King Alexander of Greece doesn't die younger there is the possibility of an union between Greece and Yugoslavia, as his only daughter Alexandra (OTL excluded by succession as born after his father's death) married King Peter II of Yugoslavia.
Albania is probably going to be governed by Zog I.
Georgia could be ruled by Prince Joachim of Prussia. He was a possibility also for Irish crown but I doubt that in a stalemate London would accept this outcome.
Former Russia is a little more difficult.
Russia itself is clearly in a Republican mood after 1917 revolutions, a Soviet or a classic one.
I spoke about Finland, Ukraine and Baltic states at the beginning of this post.
Caucasian front was a mess: if Georgia could go with a German Prince, maybe Armenia, Azerbaijan and Russian Caucasus could become a sort of kingdom ruled by Gran Duke Nicholas, grandson of Emperor Nicholas I of Romanov. Gran Duke Nicholas was the Governor of Caucasus during the revolution, Armenia was the most reluctant province to secede from Russian Empire (fear of Turks, I imagine), Nicholas promoted Islamic clerics training and save famous Islam cleric Said Nursi so this could win some sympathy among Azeris (at the opposite of Communist atheism) and North Caucasus was a strong base of White Movement, of which Nicholad was not only a member but also a candidate for the Imperial Crown of Russia. Of course, Nicholas and the Whites would continue to claim the Russian throne but, if they survive to Soviets and others enemies, it could born an informal, unofficial Kingdom of Caucasus.
Don and Kuban Cossacks States would ruled by local Hetmans.
In Central Asia we had the Emirate of Bukhara and the Khanate of Khiva.
Finally I would love the idea of Roman Von Ungern-Sternberg unites all regionalist and Whites groups of Far East and proclaims himself as new Khan of Mongolia and Siberia.