Why did you decide to make the screen 320 x 200?
320x200 pixels is a form of Mode-X VGA, which was the best available graphics mode available to Brian Fisher when he wrote the original 16-bit ASM allmodex library that the QuickBasic version of the OHRRPGCE was based on. Other resolutions are possible with Mode-X, but 320x200 with 4 "screen pages" seemed like the best solution in the early 1990's
The current version of the OHRRPGCE actually uses 640x400 resolution by default, doubling the size of each pixel. Screen smoothing filters like 2xSaI might possibly be added in future versions.