I do believe you can... I'm not a genius but I hope this web bagel will help :)
My mistake clearly, I do apologize for that, You cannot upgrade the Gpu, if you're wanting better graphics, it pays to get the newer xbox's such as the Xbox one s as it sits for Gpu: AMD GCN GPU @ 914Mhz w/ 12 compute units compared to the AMD GCN GPU @ 853Mhz w/ 12 compute units.
Which will play a small favor in looks
It has close to the same computing power its just the Xbox One X is much more powerful than the Xbox One S in central processing. It runs on eight custom x86 cores, clocked at speeds of 2.3GHz. The Xbox One S also has eight cores but they are slower, running at 1.75GHz.
Although The One X bosses things in RAM. There is 12GB of GDDR5 RAM with bandwidth of up to 326GB/s. The Xbox One S has 8GB of DDR3 RAM and 32MB of ESRAM, with bandwidth of 68GB/s and 219GB/s respectively.