Yes I was hoping for vector format so I can resize them as needed.
just tell me what's EPS in this case.

ok without kidding.
EPS is vector format.you can open EPS file in illustrator (or photoshop as mentioned previously on the thread) and resize them without any quality loss.
in illustrator just select the whole thing and resize them using the anchors
in photoshop when you open the file, it ask you wich size you want to use, give any size you want, and voila, it's resized to feet yor needs.