My mum has just got the Samsung Galaxy Tab 2.7" and was trying to set a photo as the home screen page. She did this but all it displayed was the middle section of the photo missing out the two grid sections to the left and right. Is there any way that you can set the full photo as the wallpaper?
If you're just trying to set it for home screen, try either Wallpaper Wizardrii mentioned above or Image 2 Wallpaper (com.shirobakama.wallpaper).
However if you're going for lock screen then IMO you're out of luck, at least on Samsung devices. None of the 2 above apps acknowledge Samsung's separate lock screen wallpaper and thus would not touch it.
If you're so desperate for this feature that you're willing to pay extra effort, flash non-Samsung-based custom ROMs like CyanogenMod - Tab2 has plenty of them.
I assume what is happening is that you see the left and middle of the photo on the leftmost homescreen, middle in the centre homescreen and middle and right of the photo on the rightmost homescreen.
In which case there is an app called Wallpaper Wizardrii which allows the cropping and stretching of wallpapers to fit so they don't scroll with homescreens. Check it out.