Picture Gallery Slow & Won't Refresh on HTC G2 w Android 2.3 Gingerbread
Sounds like the contents of your SD Card have not been scanned since taking the photos.  Try the SDrescan app from Market.  This should help in such situations.

Alternatively, you can manually un-mount the SD Card (via Menu -&gt; Settings -&gt; Storage -&gt; Unmount SD Card) and re-mount it again.  This should trigger the media scanner to refresh the card's contents.