Is there any way to adjust the games graphics quality other than maxing brightness and contrast? I seem to remember the visuals being much crisper/clearer than they are now.

Unable to play most of my pre win XP games after moving to win 7 in 2012 I heard of and found GOG.com in 2014 and bought Riven, URU and EOA. Later with some help I was able to re-install Exile and Revelation which worked fine in win 7.

Fast forward to 2018, now running win 10 reinstalled Riven, URU and EOA, just finished a couple 3 runs through Riven and it appears quite grainy compared to what I remember. If there are adjustments I can't find them in this new GOG setup regarding the games.

Any help will be greatly appreciated

On Windows 10 this works for me. Riven is ScrummVM game, so after starting hit ctl-f5. This will bring up the ScrummV options. Then select "return to launcher". From within there you should see an "options" button on the right side of the screen. From there you should be able to find all kinds of graphics and sound settings.

The version of ScrummVM doesn't seem to match up with all the options described on the ScrummVM Wiki, but it's better than nothing. It seems GOG is using a newer version than the "released" version on ScrummVM website.

You can search for ScrummVM graphic filter options to find the wiki that describes the graphic options. Although notably OpenGL is missing from the Wiki, but is available in the version shipped with Riven.

After playing with the options I ended up just using "OpenGL" with "Filter graphics" turned on. In windows settings I have OpenGL set to maximum quality so your results may vary.

I suppose if you're adventourous you could manually setup an even newer version of ScrummVM, though I wouldn't recommend it as I'm assuming GOG does some testing and they chose that version for a reason. Who knows, maybe they even modified it a bit.