What is best: BMP; JPEG; GIF or What?

I learned to use the OLE Object in the database table with a field called
picture. The same field is used in the input form for the table. I used a
query also with the field Picture (OLE Object) and it works just great with
the report.
So far I have only placed 5 images in the database which will have 93 more
when complete....so far the size is up to 39,952 KB. GOOD GRIEF....at this
level of growth, how can i possibly put in the remaining 93 pictures?
My question: Should I use / Can I use a smaller format of image, e.g. gif/
jpeg/tiff?
If so, how?
My pictures are in a separate folder on the "C" drive. The database uses
the OLE Object to place the "bitmap image" in the field in the
database....although as you know, the only place to see the image is in the
input form or the report.

Thanks to all who can give me a basic answer....I am a novice. I do not
understand writing code / sql / vba. Robert