It's ok to make everything the same color. I do it frequently.

I like a little contrast between walls and trim, but you could go white-on-white. In that case you may want to make the trim a little shinier like 'satin' or 'semi-gloss', and the walls more like a 'matte' or 'eggshell' (so there is a slight sheen contrast).

You have to live there, so make sure you like it.