Please my car honda accord LX came witth 15" steel wheels and front disc/rear drum brakes, i want to change the rims to 16" or17" silver alloy rims, but I noticed mine has drums at the rear instead of discs, could this still be possible?

Thanks

Very possible!
First, test fit the rim, all by itself, onto the position in question. Bolt it up and torque the wheel as you would normally and see if the wheel fits around the hub and all.
Picture the tire you want,. mounted on that wheel... Is it going to fit and how will your "ride" ride? Hmmm...
You and your car ride on the air that's in the tire. If you get a skinny tire, you surely sacrifice ride. Period.
Choices, right?