Set your graphics adapter to “S3 Inc. Trio 32/64 PCI”. That’s the one that’s being emulated by Dosbox, and it supports up to 8 MB of VRAM.
You probably need the drivers, you can either find them on your Win95 cd, or in the Win95 thread on the official Dosbox forums. Or simply google “S3 Inc. Trio 32/64 PCI windows 95 driver”. ?
Put them somewhere in your image file where you can find them. I’d suggest UltraISO for editing .img-files, you can do all you need with the unregistered free version.
And check your mounting commands. Take a look at Roland Deschains guide on xda-developers, he’s also offering pre-configured images (Win95 & Win98lite).
It’s a Dosbox Turbo thread, but DTurbo is buggy as hell, and these images also work with MagicDosbox. ?