Page 1, Panel 1 - Perseus and his winged horse, Pegasus, are characters from Greek mythology.
Page 1, Panel 3 - The body of a Green Lantern on the ground is presumably Hal Jordan, the Silver Age Green Lantern.
Page 2, Panel 1 - Here we see Kid Eternity, a little-known DC character who has the power to recall dead figures by saying the word "Eternity!"
Page 2, Panels 4-5 - The Dark Lord kills Kid Eternity before he can finish his 'magic word'. Mention is made of Metamorpho, a former JLAer who could morph into any chemical element. Metamorpho seemingly died in JLA #1 (1996).
Page 4, Panel 1 - Ramulus is an old villain of the Sandman.
Page 4, Panel 3 - Sandy meets Daniel, the Lord of Dreams. Daniel is the son of Fury (daughter of the first female JSAer - see JSA Secret Files) and Silver Scarab (Hector Hall, son of the original Hawkman and Hawkwoman). Both Fury and Silver Scarab were founding members of Infinity Inc, and before Hector died (several years ago) he was the Sandman for a brief time (after Wesley Dodds retired).
Page 6-7 - In the top panels, from L to R: Sandy (reading the eulogy), Starman, Flash, Wildcat, Sentinel, Johnny Thunder (another original JSAer, now suffering from Alzheimer's), Wonder Woman, Ted Knight (the original Starman), Star-Spangled Kid, Hourman, Atom-Smasher and Black Canary.
Page 6, Panel 2 - Why was Jack Knight (Starman) close to Wesley Dodds (Sandman)? They teamed up together in a four issue crossover between Starman and Sandman Mystery Theatre called "Sand and Stars". Furthermore, it was Wesley who revealed to Jack that years ago, Jack's father (Ted Knight) had an affair with the original Black Canary (Diana Lance).
Page 7, Panel 2 - Like Wildcat said, the original Star-Spangled Kid (Sylvester Pemberton) and the original Dr Mid-Nite (Charles McNider) were buried at 'Valhalla'. The Star-Spangled Kid, former JSAer, and founding member of Infinity Inc, was accidentally killed by fellow team-mate Mr. Bones, in a battle with long-time JSA villain, Solomon Grundy (see recap in Stars and S.T.R.I.P.E. #4). Charles McNider (Dr Mid-Nite) was murdered by Extant, along with the original Hourman and The Atom (Zero Hour #3).
Page 9, Panel 5 - Indeed, Sandy WAS "kept young for decades, due to a botched science experiment" which made him into a silicon monster. The repercussions of this were seen in Justice League of America #113 - "The Creature in the Velvet cage".
Page 9, Panel 6 - Jack asks Alan Scott (Sentinel, and formerly the original Green Lantern) about his twins, Todd and Judy-Lynn, Alan corrects him by saying 'Jenny-Lynn'. Minor point: her name is actually spelt 'Jennie-Lynn'. Both were founding members of Infinity Inc, as Obsidian (Todd) and Jade (Jennie-Lynn).
Page 10, Panel 1 - Here we see Obsidian in his civilian identity - Todd Rice.
Page 10, Panel 5 - "Call me Ian." Who is this mystery villain, trying to 'corrupt' Obsidian? See the "Darkness Falls" saga, upcoming in JSA #7-9.
Page 11, Panel 1 - In the corner is the gravestone of the Crimson Avenger, who was the first recognized 'Mystery Man' of the Golden Age. Furthermore, he was a member of the Seven Soldiers of Victory, a Golden Age team which also counted the Star-Spangled Kid and Stripesy among it's members. For more on the Crimson Avenger, see the Crimson Avenger page.
Page 11, Panel 3 - Jay sees an apparition of Kent Nelson, the original Dr Fate, and fellow founding member of the Justice Society of America.
Page 12, Panel 1 - Fate, the latest to hold the legacy of Dr Fate (albeit loosely), enters beside the grave of the Red Bee, another Golden Age hero.
Page 13, Panel 3 - A brief origin of Fate is given here. For more information on Jared Stevens (Fate) or other incarnations of Dr Fate, read the profiles at The Immortal Doctor Fate webpage.
Page 13, Panel 4 - A minor correction: Wesley Dodds wasn't murdered by the Dark Lord - he committed suicide (JSA Secret Files). However, it is possible that Jared Stevens just PRESUMED Wesley had been killed, without knowing for sure.
Page 17, Panel 2 - Johnny Thunder considers calling the Thunderbolt, the 5th-dimension genie that accompanied him for many years. Johnny could call the Thunderbolt by saying the magic words, "Cei-U!" (Say, You!). The T-Bolt now resides with youngster, JJ Thunder (JLA #28-31).
Page 20, Panel 2 - Mention is made of the "Cycle of Khepri", which evidently relates to Khepri, the Egyptian God of Rebirth.
Page 22 - We are introduced to Scarab (not to be confused with Silver Scarab, Hector Hall, mentioned previously). Scarab's real name is Louis Sendak, who was mentioned in JSA Secret Files (Page 3, Panel 2 - Sandman:"You'll contact Sendak?"), and his power comes from the Scarabaeus on his chest, which is the sacred amulet of Khepri.