@Jayta: By reusing images from other presentations, do you mean presentations that were created by other members (i.e., from the BrillKids Library)? If that is the case, it is best that you ask the file author for permission first. We do have a "collaboration" feature in place when uploading a file to the library, so you can use that if the other member agrees to let you use some images from his/her file.
In cases of copyrighted material, we recommend that you clearly state where you got your images or other media files from in your file's description. You can upload as many files as you like, but kindly keep in mind that we may take your file down upon the request of the respective copyright owner(s). Also, Little Reader and Little Math files which contain copyrighted materials are not eligible for the Premium file status (we don't have this status tier for the free downloads section at the moment).
Here are some pointers you may refer to:
http://forum.brillkids.com/little-reader/brillkids-criteria-for-approving-little-reader-files-as-premium-content/@Mario: If you can remember it, what exact error message did you get? There is a green "Add Download" button at the upper right part of every page in the library (except for the library's home page) - it is best that you upload your files in the Library instead of here in the forum.
Just click on the "Add Download" button and you'll see a page where you can fill in the details about your file and also to upload your file. If you encounter any problem or an error message in any page in the library, please do let us know so we can fix it as soon as we can.