The 28-year-old made 10 appearances during a three-month loan spell with the Lions earlier this season and has recently been the subject of a bid from boss Kenny Jackett to sign him permentantly.
That offer was turned down, though, and Jackett has since indicated he is unlikely to return with an improved bid.
But Howard, who has yet to make an appearance for Reading since returning to the Majdeski Stadium, insists he is still keen to re-join Millwall if a deal can be struck with the Royals.
"I hope to re-sign for Millwall and I love getting games under my belt," he told the Barnsley Chronicle. "The fans are mad and passionate and Kenny Jackett and his team are brilliant coaches.
"They need a bit of luck in front of goal but they have some quality players and should be higher in the league than they are."