The Flash is a fun television show, but you know what would make it even more fun? If they took some inspiration from these Silver Age Flash covers.
The Flash #112 (April-May 1960), "The Mystery of the Elongated Man!"
They already name-checked Ralph Dibney as one of the people who died in STAR Labs. It wouldn't be that hard to pull a Firestorm and have him actually have survived — only with stretching powers.
(Which would be an improvement over the way he got his powers in the comics: he learned that all contortionists drank a special soda called "Gingold" and then made a concentrated extract of the fruit it was made from and bam, elasticity.)
The Elongated Man was always one of the Flash's oldest and best friends and often provided backup stories where he and his wife, Sue, solved mysteries.
The Flash #123 (September 1961), "Flash of Two Worlds!"
Even though Jay Garrick lived on a parallel Earth during the Silver Age, he was always an important member of the Flash's friends. In fact, he was the inspiration for the Flash — due to some weird cross-world thing, Jay Garrick's adventures as the Flash were published as comic books in Earth-1 and that's where Barry Allen took the name.
In the show, they've already shown how vibrating fast enough can cause Barry to travel back in time. It's just a short leap from "time travel" to "parallel Earth travel," right? Because seeing Jay Garrick as the Flash would be nothing short of awesome.
The Flash #124 (November 1961), "Space-Boomerang Trap!"
I mean, I really just want to see Barry strapped to a giant boomerang.
I know it doesn't make any sense, but...come on. You know you want to see it, too.
The Flash #133 (December 1962), "The Plight of the Puppet Flash!"
There are two reasons I want to see this cover on the small screen:
1) Abra Kadabra would be an awesome supervillain. He's another person from the future — although while Eobard Thawne is from the 25th century, Abra is from the 64th and really just wanted to be a stage magician (even if he did use future inventions to hypnotize the crowd).
Also, after someone says his name, someone else must reply, "Gonna reach out and grab ya."
2) We need to see Barry turned into a puppet. It could be like "Smile Time" all over again.
The Flash #153 (June 1965), "The Mightiest Punch of All Time"
Just imagine how awesome that would be:
Barry punches the Reverse-Flash so hard that doesn't knock him into next week, he knocks him five hundred years into the future.