The most important I think is does it have commercial value and then composition and light. After that you can do the noise etc. You can have a perfect image but if it has no commercial value no amount of adjustment is going to make it work for stock.
Composition and light are vital....a dull photo is of no use either.
If we specifically talk about dreamstime.com, I have to say that "they pay for art!" which deserves a big applause. Many other stock agencies don't accept artistic photos, but I have some really low quality, good composition artistic shots uploaded and accepted here...and they don't have that much commercial value. Here is an example...
As an addition to what my colleagues mentioned above, you should leave some copyspace for designers and check the image for copyright protected buildings, products, brand names etc.
Hongtao926, thats the million dollar question you are asking...
You may separate it in two so it gets easier to find a solution.
On the technical side, minimum resolution is 3Mpixels, the subject of the image has to be in focus, there should be no gaps in the histogram, no purple fringe, lens difraction or lens distortion.
On the composition, you should have a composition that add to the point of your image, and that´s the tricky part.
Consider Parkinsonsniper excample, if the subject is the nail polish, than the picture is perfect, if you are trying to sell lipstick, ... You should read some books about composition, Michael Freeman The eye of the Photorapher would be a nice one to take a look, for instance.
Now, the thing is, everything in the image needs to be focused on emphasizing your concept, so, even technical "errors" are ok if that´s the concept you are emphasizing, I mean, drunk with lack of focus, sparkling with some glare, speed with motion blur,..., I hope I am making myself clear here.
Now, since you are starting, is better to stick to the basics, I mean, make it plain and simple as a start, use the rule of thirds, fix the verticals, 3/4 lighting not harsh, than you add more complexity, backlight, side light, and other stuff, I tend to think it as an adding process.
I like to take travel images, normally I go first for the more basic stuff, so, I calculate the hour when the light will be good and visit the place, first basic images, than I start looking for diferent angles, wide angle lenses, a diferent foreground, relationship between the background and the subject, a reflection, etc. Many of those experiments end up in my trash can, but some are my favorite images!
If I dont do that, I will be back with some amazing "diferent" images, but the plain thing that sometimes is the one who sell more I wont have...
This is one of my best sellers, its an ok image, I have some others from Santiago do Chile that are much more thrilling though, but there is no way any magazine talking about Santiago won´t have an image of Palacio de La Moneda.
I think best way to identify photo is good or bad, is look on your own photos like a buyer. Even better is think about photos like potential buyer before taking photos.
Then I have one practice. I don't look at my photos only in 100% enlargement (my favorite is 300% scale). During selecting and retouching photos, I am looking on small thumbnail and many other scales (thank this I see different levels of details). But looking at the thumbnail size is especially important, because I see how photos see buyers at first time. When I look on thumbnail size, I must be able recognize message of photo. If I am not able recognize message, buyer will not be also.
Who Knows??? Aside from the technical advise already given, it's a crap shoot. When I was first starting here, I got so frustrated getting rejections on what I thought would make a good stock photo I uploaded this one as a kind of joke. To my surprise it was accepted and is now a level 5!!!! Keep submitting and, maybe, you will get a clue as to what makes a good stock pic. When you find out, please post your findings. Good Luck!!
Quoted Message: Who Knows??? Aside from the technical advise already given, it`s a crap shoot. When I was first starting here, I got so frustrated getting rejections on what I thought would make a good stock photo I uploaded this one as a kind of joke. To my surprise it was accepted and is now a level 5!!!! Keep submitting and, maybe, you will get a clue as to what makes a good stock pic. When you find out, please post your findings. Good Luck!!
WOW I just did a reverse image search on this image to see how it was used and almost every result showed misuse of the image with the DT watermark still on it!!!!!!
I just typed in the title on google images and it was the first one. Anyone can copy it. What is my next step? The link to it had no DT watermark but it has a link to copy it. Also found it on another blog with logo on it. No DT watermark on google images.
Quoted Message: Godfer, how did you do that? I suspected this one was being misused :) How do you do a reverse image search?
On Google Images, there is searching form. On right, there is a small gray icon of photo camera. Click on this small icon. There is new form where you can paste URL adress of image (JPG file, not HTML where image is) or upload image.