Where do i get free wallpapers for my phone?

Congratulations on your new purchase of Samsung mobile. From your query, it appears that you have bought a Android based device manufactured by Samsung. Android offers a lots of choices in customizing the operating system, especially comparing to the competition like iOS or Windows Phone. It would've been a bit more easier if you had a working computer but that should not stop you from downloading and using new wallpapers on your mobile. There are a huge number of websites that can help you to get your mobile a new facelift. To name a few, there are DeviantArt, Interfacelift etc. These websites often have wallpaper collections specifically made for a particular phone or a series of models. Choose the one of your liking and set as wallpaper on your mobile. Sometimes, there are wallpaper packs that come with a archived file like .zip or .rar. As I said before that it would've easier to unpack them if you had a working PC but fear not! Android also has Unrar and Unzip apps available on Android Market, and most importantly both of them are completely free. Just install them and unzip/unrar that wallpaper collection you may just have downloaded and you'll be ready to go.

If you're past the initial levels and ready to go for the extra miles, then I recommend you to root your Android device and go for additional themes that are available throughout the internet. DeviantArt is a good source for such themes, so is XDA Developers website.