Well, I agree that the shown fabric is good for Wedding or Christmas,
thank you all , I'll choose a subject according to your advice.
I still want to try stitching on linen with square holes, as purple-footprints said, and see what happened when someone choose not special canvas.
Thank you Rose for detailed recomendations with the colour of canvas.
I should say that I don't like white canvas and always try to change the colour especially when the stitched character is white, for example, a bear or geese. When I stitched the white garden bear by Dimensions I choose ecru canvas and when I had it framed I saw that carver and gilder put under the stitched picture green paper so the canvas changed the colour. It became greenish but it looked fine because the frame was also green. The white bear stand out against a background and looks even whiter.
I absolutely agree with purple-footprints, that it is harder to choose the bright color then the pastel one. Naturally you can just try to imagine the finished pattern and to see where you will hang it up. There is such concept as cold and warm colors. And you changing the background can make the picture suit your flat design

. And also there are some designs which colors you can't change, for example this one

A word is dead when it is said, some say.
I say it just begins to live that day.
Dickinson E.