The number of images will depend on the quality setting and image size. 512 MB is pretty small. I'd go for a 2 GB and use the 512 for a backup. But that being said it would be between 120 and about 430 pictures.
See the Question: How many pictures on 4GB memory card in 10.2 mega pixel digital camera?(How_many_pictures_on_4GB_memory_card_in_10.2_mega_pixel_digital_camera)
1GB MEMORY CARD CAN HOLD 150 TO 200 SNAP IN A 13.6 MEGA PIXEL CAMERA.
A camera with this pixel setting will have more room, but the images may not be as crisp as ones with a bigger pixel count. You can fit approximately 200 pictures of this kind on a 2 GB memory card.
200
417
Roughly 200.
256
60000
About 6-8 photos.
It will hold up to 1,164 8 mega pixel images. However, the settings on the camera can be changed so that the camera takes pictures of a different size. The same memory card can hold over 4,000 2 mega pixel images. Changing these settings will affect the quality and size of the pictures you take.
It depends on the format. In JPEG, it's around 18.
The content of the picture and what "Quality" level you are using affects how many pictures a memory card will hold. A 2 GB card in a 7.2 MP camera will hold something like 800 pictures on medium quality and 400 pictures on high quality.