=IF(ISTEXT('Sheet1'!A1), "*", IF(ISBLANK('Sheet1'!A1),'Sheet1'!A1, IF('Sheet1'!A1 >= 10, IMAGE("https://docs.google.com/drawings/d/1zvwx-srTZlBYQgO1KNdx9-aB1Bw-GRXCfByBPmW0X_M/pub?w=120&h=90"), IF(AND('Sheet1'!A1 < 10,'Sheet1'!A1 >= 7.5), IMAGE("https://docs.google.com/drawings/d/1YlsedUl2v81KzJjGrmDu90f7Kvc-C4sMQ_EnM40Eei4/pub?w=120&h=90"), IF(AND('Sheet1'!A1 < 7.5,'Sheet1'!A1 >= 5), IMAGE("https://docs.google.com/drawings/d/1IFZiKmFa8zv_7XYxBkIrbJOb_QthS5aNP_VPs3sPbx4/pub?w=120&h=90"), IF(AND('Sheet1'!A1 < 5, 'Sheet1'!A1 >= 2.5),IMAGE("https://docs.google.com/drawings/d/1P0ZZ6bbx1xnhaIDKU34XY_rGzfZIcDbN-dycneMlZ1k/pub?w=120&h=90"),IF('Sheet1'!A1 < 2.5,IMAGE("https://docs.google.com/drawings/d/1gTEKIQuY29SB1HCrcDiT31D0ZsaWaUVMBW_ZW5sjGow/pub?w=120&h=90"),'Sheet1'!A1)))))))
NOTE: "Sheet1" should be replaced with whatever the target sheet name actually is in your Google Sheets document