I'm not convinced Kitchens will be fired, but if he is, here's a list of pretty much any possible candidate broken down into three tiers.
Former NFL Head Coaches
Mike McCarthy
-56 years old, 125-77-2 career record, 9 playoff appearances in 13 seasons, currently unemployed
Ron Rivera
-57 years old, 76-63-1 career record, 4 playoff appearances in 9 seasons, currently unemployed
Jim Caldwell
-64 years old, 62-50 career record, 4 playoff appearances in 7 seasons (*), currently Dolphins AHC/QB
Marvin Lewis
-61 years old, 131-122-3 career record, 7 playoff appearances in 16 seasons, currently special advisor at Arizona State University
Josh McDaniels
-43 years old, 11-17 career record, 0 playoff appearances in 2 seasons, currently Patriots OC
Leslie Frazier
-60 years old, 21-32-1 career record, 1 playoff appearance in 4 seasons, currently Bills OC
Jim Schwartz
-53 years old, 29-51 career record, 1 playoff appearance in 5 seasons, currently Eagles DC
Steve Spagnuolo
-59 years old, 11-41 career record, 0 playoff appearances in 3 seasons, currently Chiefs DC
Dennis Allen
-47 years old, 8-28 career record, 0 playoff appearances in 3 seasons, currently Saints DC
Current NFL Coordinators/Position Coaches
Dan Campbell
-43 years old, Saints AHC/TE (*)
Matt Eberflus
-49 years old, Colts DC (*)
Nick Sirianni
-38 years old, Colts OC (*)
Kevin Stefanski
-37 years old, Vikings OC (*)
George Edwards
-52 years old, Vikings DC
Eric Bieniemy
-50 years old, Chiefs OC
Dave Toub
-57 years old, Chiefs STC
Brian Daboll
-44 years old, Bills OC
Mike LaFleur
-32 years old, 49ers PGC
Mike McDaniel
-36 years old, 49ers RGC
Robert Saleh
-40 years old, 49ers DC
Don Martindale
-56 years old, Ravens DC
Greg Roman
-47 years old, Ravens OC
Byron Leftwich
-39 years old, Bucs OC
Kellen Moore
-31 years old, Cowboys OC
Kris Richard
-40 years old, Cowboys DPGC/DB
Shane Waldron
-40 years old, Rams PGC/QB
Joe Judge
-37 years old, Patriots STC/WR
Current/Former College Head Coaches
Matt Rhule
-44 years old, Baylor
Lincoln Riley
-36 years old, Oklahoma
Jim Harbaugh
-55 years old, Michigan
Urban Meyer
-55 years old, formerly Ohio State
Dan Mullen
-47 years old, Florida
Matt Campbell
-40 years old, Iowa State
(*) indicates candidate previously interviewed with Browns within the team's last two hiring cycles.
Also worth noting, the Browns also interviewed these five NFL head coaches within their last two coaching hire cycles: Matt Patricia (Lions), Doug Marrone (Jaguars), Sean McDermott (Bills), Adam Gase (Jets), Brian Flores (Dolphins).