The image you're uploading needs to be in a recognised image format, such as .jpeg or .bmp. What's probably happened is that you've tried to upload an image file that you saved from your editing program, and so it's saved as something like .psd or .psp. In which case, when you save your image, you'll want to change the file type when you save it, .jpeg should do.

Hope that helped

Its file type is .jpg

@CheeseyBricks, I haven't edited the photo at all and it says that it is .jpg. Would that file type work? Or do I have to change the file type?

Never mind. I figured it out. Thanks for the help everyone.

Remember that real people have to watch, rate, and review every film that is processed through the submission page. We (the review panel) have a lot of films to go through, and the queue (the number of films in line, waiting to be reviewed) was at 180 or so a month ago. We've actually cut that number in half with the review panel expansion, and are working towards making that number as small as possible.
That said, it could still be another week or two before your film is reviewed. Just be patient.

Okay, sorry. I didn't know that there were so many people wanting to submit their movies!

No, you just have to check.

BRAWL 2013 ENTRY Quack In Time
"Why in the world did you do a weird language if you know English?" - tenny1028

Hey guys I just signed up here and am trying to post my film but it keeps saying "Sorry, you failed to upload a thumbnail image for your film. Please go back and correct this. " and I've uploaded an image and can see it in the preview box, what should I do to fix this, oh and it's a jpeg.

Thanks for your help, I figured it out now, but which contest do you know me from? I figured that when I signed up here no one would know me.

It depends. Two to three weeks is usually a pretty standard wait. We have 159 films in the queue at the moment and many of the reviewers have the beginning of the school year to contend with.