Question: I just want to know how to get images from other web page and show in my website.

Case flow is:

1. Type some page URL in text box and submit
2. Collect all images in that web page (not in entire site) and show them in my webpage

Answer: 
If you want do scrape other websites with javascript, you should create a server side script which can act as proxy or you can use YQL.

Here's my answer for cross domain ajax call with YQL,

[Cross Domain Post method ajax call using jquery with xml response](https://stackoverflow.com/questions/11239584/cross-domain-post-method-ajax-call-using-jquery-with-xml-response/11240217#11240217)
First of all check for Copyright. Copy only if the image is provided by the owner for free use. Also read and understand the license of usage.

If the image is free to use as stated by the owner under license then download the image and then use it. Also, please don't forget to keep copy of the license and the website url from where you downloaded the image.

Download and then use is suggested so that if tomorrow the other website shuts down then your website remains unaffected. 

Last but not the least, try to design/ shoot your own images. Even if they are not as good as others at least they are genuine.