You will need Photoshop. Faster version without dependency on Photoshop.
- Open texture in Photoshop.
- Convert .jpg and .jpeg textures to .png to prevent quality loss on subsequential reassemble of texture. It is recommended for any lossy format, if you do not know what type of format it is convert it to .png.
- Next select Slice Tool.
- Draw slice in center of texture
- Next delete this slice, right click on this slice area. You will left with one big slice, sized to whole texture. You may try to right click on image without creating and deleting slice, this instruction written more safely.
- Next click right mouse click on this slice, sized to whole texture, select Divide Slice.
- Next input Horizontal, Vertical row counts, press OK.
- Next click File -> Export -> Save for Web.
- Alt+Mouse Scroll to zoom out from texture preview or you can use percent in left bottom corner. Then drag box to select all pieces, select PNG-24 present, disable transparency if needed.
- Click Save, pay attention to Slices option.
- Now you have separate images for pieces. You can reassemble texture using Rw-designer.com, click on Rearrange to change columns count. Or replace card right in the texture, using original card size, image.