Vanakkam,
This is how I do Vinayaka Ji, I have put pictures so it can be more clear, I hope it help:
First, find the picture you want on internet. You should have only the picture displayed, not the entire website.
Copy the adress of the picture
You know it's the adress of the picture and not of website when there is things like .jpg or .png or .gif in the end.
After you have copied the link, on the reply to tread, click on the picture with a montain here:
Past the link of the picture you previously copied on the box that appear:
You should then have the picture displayed !
How to find the picture adress on a website ?
If you are on a website and see a picture that have interest for you and want to share the same manner as above, the problem is you cannot copy the link. Because it is the link of the whole website and not of the picture. Therefore, it is either too long or invalid when you enter it on the forum.
So, right click on the picture and you should see on the menu something like "Display picture"
(I am sorry it's in french, but the translation should be something like "display picture")
Then, clicking on this, you should now have the picture only opened in a new frame, you can now copy the adress of the picture
I hope it help _/\_ may not be the most perfect manner to do so but....It kinda work so...
Aum Namah Shivaya