Hi Nikhil,
In the get_p method of the attribute, make it field_type_image.
In get method of the attribute, based on conditions set the values as follows
IF ls_attr-pso_status = '2'.
value = '/SAP/BC/BSP/SAP/thtmlb_styles/sap_skins/default/images/green_light.gif'.
ELSEIF ls_attr-uho_status = '3'.
value = '/SAP/BC/BSP/SAP/thtmlb_styles/sap_skins/default/images/red_light.gif'.
endif.
hope this helps 