Was this king mentioned elsewhere?
Malbim, from Vayikra Rabah 18:2: This is Chiram, the friend of Shlomo. He lived until that time, and Nebuchadnetzar killed him. Another Midrash (Yalkut Shimoni Lech Lecha 76) says that Chiram entered Gan Eden while alive. The Midrashim learn from the verses here.
Malbim: Simply, Chiram in the days of Shlomo received great honor via his Bris with David and Shlomo, and he helped to build the Beis ha'Mikdash. He merited to dwell in the lower Gan Eden, like all Chasidei Goyim. He has 10 canopies there. After he died, his nation did not accept another king; they appointed a Nagid to conduct the country. They made an image of Chiram sitting on his throne with 10 canopies over him from gems, like he sits in Gan Eden. They also drew his flag in the form of a Keruv made from olive wood, over the Aron. Since two such Keruvim were made, they say that one hints to Shlomo and the other to Chiram, who was a partner in building [the ha'Mikdash]. This Parashah discusses this image. Or, they put a Chacham 'in place of' Chiram and called him Melech Tzor; he did not run the country, rather, the Nagid did. After prophesizing about the Nagid, the Navi discusses Melech Tzor, who was divine and Kadosh to them.
What is the meaning of "Atah Chosem Tachnis?"?
Rashi: You are full of Chachmah to seal and fix every form.
Radak: You complete the plan; all is complete in you. Tachnis is a noun with the grammatical form of Gafris. The [first] Tov is from the root. The same applies to "u'Madedu Es Tachnis" (43:10). [You are] the content of all Chachmos, honor and wealth ? "Malei Chachmah u'Chlil Yofi."
Radak citing Targum Yonasan: You resemble a Kli whose form was fixed with Chachmah, and is complete in beauty.
Malbim: Even though you are not Chiram, just his form is carved into you, your form is proper. You do not lack anything ? you are full of Chachmah and beauty. This can apply to the king in place of him, or his image (refer to 28:12:1:2).
