Page 2, Panel 2 - Tylerco is the company founded by the late Rex (Hourman I) Tyler (see also JSA Secret Files lead story).
Page 4, Panel 1 - Dr Iker is a former Golden Age foe of the original Hourman. Although this issue mentioned that the original Hourman fought Dr Iker sometime in the 1940s, I don't believe this particular story (with clones dwarves) has been reprinted since (Credit: Graeme Fitzgerald).
Page 6, Panel 1 - Here we are introduced to the NEW Mr Terrific, Michael Holt whose first appearance (albiet, with a very different costume) was in the Spectre #54. For more information on Michael Holt, or the original Mr Terrific, see: The Unofficial Mr Terrific Homepage.
Page 6, Panel 4 - Sand: "Sounds like you're doing Terry's memory justice....." This is a reference to Terry Sloane, the original Mr Terrific, who Sand has worked with in the past.
Page 8, Panel 2 - The man in the wheelchair is John Stewart, who is a former Green Lantern (he filled in for Hal Jordan). John is also a former Darkstar. He first appeared in GL (second series) #87, 1972. John Stewart's companion is Merayn, a former colleague from his days as a Darkstar. (Credit: Graeme Fitzgerald).
Page 14, Panel 4 - Geomancer mentions "some outfit called the Council". Perhaps we'll find out who they are in the future? Presumably, 'the Council' could relate to a new Injustice Society...........
Page 18, Panels 5-6 - Sand applies a sleeper-hold to Geomancer, temporarily shutting off the flow of blood to his brain, so that he loses consciousness. Sleeper-holds are predominantly used in professional wrestling.
Page 19, Panel 4 - Here we see Sand's new costume, keeping a variation on the Sandman's gas-mask, while adopting new bodywear, for travelling underground (without ending up naked every time! - see earlier this issue).
Page 21 - The man seated is Jim Rice, the abusive foster-father of Obsidian (Todd Rice), who is the natural son of Alan Scott (Sentinel).
Page 22, Panel 3 - Obsidian: "Don't worry, Ian." There's that name again......(see #1, page 10)