this can be pushed much further.  I did an edit, Ill try to explain everything I did

first thing I did was get rid of the dithering.  Its not really serving much purpose here.  Dithered texture doesnt make sense for a liquid, and the effect of extra colors is so minimal here, due to low contrast, that it isnt actually that noticable anyways.  Especially in the rim of the cup where you dithered the two light greys.  Those greys are so similar to eachother you dont even need one of them.

Next, the words on the cup isnt very noticable.  I made the words white so they stood out more.  Alteratively, you could make the blue around it lighter.

Most importantly, I got rid of the black lines on the inside.  The outline isnt needed around the logo, and kind of flattens the rim.  You can get a better rim by getting rid of the black and using some AA.  I also got rid of the black lines on the outside, but you could potentially keep those as stylistic choice.

I didnt take time to do any palette optimizing but the palette could stand some optimizing.  Notice how I used the lightest brown from the coffee to add another shadow color to the yellow part of the cup.  Thats an example of how you could share colors in different parts of the image to make a more optimized palette.  Notice also that that extra shadow, and the darker shadow on the rim gives it increased contrast and makes it seem less flat.

I also added some AA, a shadow and some steam just to make it more interesting.  And I think thats pretty much it.