why do I have problems with inserting photoshoped photo in solidworks

What is the file format you are trying to insert? I never use labels in SOLIDWORKS, but if I did, I'd convert the image to a PNG file and try again.

That said, I did try to insert a PSD file as a label and it worked. It took a minute or two before it showed up on the model, but it worked.
looking deeper into the issue, SW converted the selected PSD file into a BMP, and save the BMP into the decal library.

Do the conversion yourself. Just save your PSD as a PNG (or other "normal" image format). Then apply it as a decal.

As a self-taught Solidworks rookie, I've been inserting images by editing the appearance of a face and applying/mapping the image. I typically use jpeg or bmp formats. (I'm adding safety signs to a machine)

Is this OK, or are Decals better?

Jack,
I have to admit that I use neither, but I did just fiddle with both options for a few minutes. If I had to choose one, I'd pick labels.
Labels appear to give additional control regarding the mapping, tiling, masking, rotation, and they are a lot easier to save and reuse again.

I think a decal is best for things that are best represented by a single decal or sticker. I.e placing a sign on a model.
Appearances look to be a better choice for placing a "texture" over a larger surface like making a wall look like brick, or putting stripes on a chair to make it look more like nylon webbing.

Thanks for all your answers.
I tryed with JPEG, PNG and PSD formats but it didn't work. I will upload my model and the picture and you can try.
Thanks

Decals in SOLIDWORKS are hard.
I don't know why, but don't use a transparent PNG. It makes perfect sense to use one, but it is not working right. I assume it has something to do with how the file is saved, but try a bmp, tiff, or jpg instead.

Attached is an image I did with a bmp of the label, plus a mask. The same could likely be done with a transparent tiff, but PNG worked so well, I did not bother trying.

Also attached is the label and mask I used.
As well as a quick rendering from Keyshot. Keyshot had no problem with the transparent png file.

Thanks a lot!
With what program did you change my photo to the attached one (original)? Because if I try with photos that you attached it works perfectly but if I change it to bmf it doesn't work

Any photo edits would have been done in one of two programs though.
Photofilre: http://www.photofiltre-studio.com/pf7-en.htm (freeware)
Or PhotoShop.

If I recall correctly, I saved your png file as a bmp in PhotoShop. I'm not sure though, I had a few models happening at once.

Sometimes I'll also use VectorMagic to convert raster images into a vector format, or even just to cleanup an image. I'm 75% certain I saved the above bmp files out of Photoshop though.

If I'm not asking too much, can you please do it with this picture and model as well because it doesn't work if I do it exactly as you said.
Thanks

The jpg works fine without any modification or re-saving.
Here is a quick video of it in action: http://www.filehosting.org/file/details/749846/capture-1.avi

Use a temp email address from https://10minutemail.com or a similar site.

I apply one of the default labels, then replace the image being used with another. Just make sure to select No Mask if it is turned on be default.

Nice, I finally found what was the problem. I think it was the sibilant in the name of the picture.
Thanks to all of you!