I would suggest using ImageMagick to generate an index page for each directory with a command line, (probably better put into a batch file or script), such as:
montage -label '%t\n%[width]x%[height]' \
-size 512x512 "../img_photos/*.*[120x90]" -auto-orient \
-geometry +5+5 -tile 5x -frame 5 -shadow photo_index.html
Then you would get results such as this web page which looks like, example from the site:

ImageMagick is:
- Free, Gratis & Open Source
- Cross Platform
- Supports over 200 file formats, (depending on your platform & installed libraries), including:
- ARW - Sony Raw
- CR2 - Cannon Raw
- CRW - Cannon Raw
- DCR - Kodak Raw
- MRW - Sony (Minolta) Raw
- NEF - Nikon Raw
- ORF - Olympus Raw
- RAF - Fuji CCD-RAW
- RW2 - Panasonic Lumix Raw Image
- SR2 - Sony Raw 2
- SRF - Sony Raw
- X3F - Sigma
- Numerous other batch processing operations.
It does take a few minutes and you may need to tweak the command &/or the resulting html map but it only needs to be done once per directory and effectively gives you a "Contact Sheet" of that directory.