A complete search of the internet has found these results:
Looking forward to seeing you tonight is the most popular phrase on the web.
Both of these phrases have the same meaning and usage. "I look forward to seeing you tonight" is technically more grammatically correct, but both phrases are commonly used.
2,079,937 results on the web
Looking forward to seeing you tonight, honey!
I haven't seen you in ages. Looking forward to seeing you tonight for dinner.
Did you say you were looking forward to seeing him tonight, or is that tomorrow night?
Looking forward to seeing all of you tonight at the party. Stay safe!
Dillan says that he is looking forward to seeing all of us tonight.
I'm not exactly looking forward to seeing you tonight, but I hope everything goes well.
1,008,600 results on the web
I look forward to seeing you tonight at the office party. It only comes once a year!
He stated, "I look forward to seeing you tonight" to the entire office staff.
The actress screamed, "I look forward to seeing you tonight after the show is over." It wasn't part of the script.
I look forward to seeing you tonight, where we shall catch up on old times over some drinks.
I look forward to seeing you tonight and relaxing after all the crazy stuff that has happened this month.
I'm really sorry to say this, but I do not look forward to seeing you tonight after all that we've been through.