This question comes up quite often in the forums, I am sure if you do a little searching you will find the answer to your questions.
Here is one recent thread which may help...
Here are some other gallery type sites I found in the 'DreamHost Site of The Month' section of the Web Admin Panel.
Overall, I doubt you will see quite the same speed on any shared hosting as you do on your dedicated machine, but personally I have never run into a speed problem here on DreamHost.
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