Graphics for wordpress theme

I am looking forward to make some changes in my wordpress blog theme. Main changes are graphic related. I have a problem in changing graphic because whenever i design a graphic to replace the old one it is more than 20 KB but the originals are 1 to 3 KB so the new graphics take time to load how should i save my new graphics in photoshop so that they have small size

 

You should save your images using the "Save For Web" function - they will be smaller as when saved with pure Save/SaveAs.
Further steps depend on whether your images are JPGs or PNGs/GIFs.

 

Few things can be done:
1) If you save under .jpg format, while saving it will ask u to save in different type of quality. Choose the type with lower file size.

2) You can also consider saving with .png or .gif .

 

Hmm thank you very much azlanhussain and Varelse
I am also thinking about one more thing. There are some graphics which are used in different places seperatly but are saved together. I mean look at these attachments.
In first attachment, Previous and next buttons are on the left and right corney of blog page but they are saved in one file.
In second attachment, These green small buttons are used seperatly (one at a time) but are saved as group
any Idea about this

 

These icons/buttons are saved as a one file and they're "cropped and positioned" with styling sheets. If you don't want to edit your layout code, you have to follow the grid of such a composite image when you are replacing its parts.

 

Oh ok
so should i just open them in photoshop, edit them keeping same size and resave them

 

Exactly. Also when editing them be careful not to cross the lines between two neighboring buttons.

 

Hmm Awright you was a great help bro